1
|
Tozer DJ. Effective homogeneity of Fermi-Amaldi-containing exchange-correlation functionals. J Chem Phys 2023; 159:244102. [PMID: 38131479 DOI: 10.1063/5.0179111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Accepted: 11/30/2023] [Indexed: 12/23/2023] Open
Abstract
Parr and Ghosh [Phys. Rev. A. 51 3564 (1995)] demonstrated that when near-exact electron densities and potentials are used, the exchange-correlation energies of first- and second-row atoms are well-described by a combination of the Fermi-Amaldi functional with a functional that is homogeneous of degree one under density scaling. Insight into this observation is provided by considering their work from the perspective of the effective homogeneity of the overall exchange-correlation functional. By considering a general form that combines the Fermi-Amaldi functional with a functional that is homogeneous of degree k, it is shown that for these atoms, the functional of Parr and Ghosh (k = 1) exhibits essentially optimal effective homogeneities on the electron-deficient side of the integer. Percentage errors in effective homogeneities are close to percentage errors in exchange-correlation energies.
Collapse
Affiliation(s)
- David J Tozer
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, United Kingdom
| |
Collapse
|
2
|
Taylor JT, Tozer DJ, Curchod BFE. On the description of conical intersections between excited electronic states with LR-TDDFT and ADC(2). J Chem Phys 2023; 159:214115. [PMID: 38059547 DOI: 10.1063/5.0176140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Accepted: 11/14/2023] [Indexed: 12/08/2023] Open
Abstract
Conical intersections constitute the conceptual bedrock of our working understanding of ultrafast, nonadiabatic processes within photochemistry (and photophysics). Accurate calculation of potential energy surfaces within the vicinity of conical intersections, however, still poses a serious challenge to many popular electronic structure methods. Multiple works have reported on the deficiency of methods like linear-response time-dependent density functional theory within the adiabatic approximation (AA LR-TDDFT) or algebraic diagrammatic construction to second-order [ADC(2)]-approaches often used in excited-state molecular dynamics simulations-to describe conical intersections between the ground and excited electronic states. In the present study, we focus our attention on conical intersections between excited electronic states and probe the ability of AA LR-TDDFT and ADC(2) to describe their topology and topography, using protonated formaldimine and pyrazine as two exemplar molecules. We also take the opportunity to revisit the performance of these methods in describing conical intersections involving the ground electronic state in protonated formaldimine-highlighting in particular how the intersection ring exhibited by AA LR-TDDFT can be perceived either as a (near-to-linear) seam of intersection or two interpenetrating cones, depending on the magnitude of molecular distortions within the branching space.
Collapse
Affiliation(s)
- Jack T Taylor
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, United Kingdom
| | - David J Tozer
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, United Kingdom
| | - Basile F E Curchod
- Centre for Computational Chemistry, School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, United Kingdom
| |
Collapse
|
3
|
Teale AM, Helgaker T, Savin A, Adamo C, Aradi B, Arbuznikov AV, Ayers PW, Baerends EJ, Barone V, Calaminici P, Cancès E, Carter EA, Chattaraj PK, Chermette H, Ciofini I, Crawford TD, De Proft F, Dobson JF, Draxl C, Frauenheim T, Fromager E, Fuentealba P, Gagliardi L, Galli G, Gao J, Geerlings P, Gidopoulos N, Gill PMW, Gori-Giorgi P, Görling A, Gould T, Grimme S, Gritsenko O, Jensen HJA, Johnson ER, Jones RO, Kaupp M, Köster AM, Kronik L, Krylov AI, Kvaal S, Laestadius A, Levy M, Lewin M, Liu S, Loos PF, Maitra NT, Neese F, Perdew JP, Pernal K, Pernot P, Piecuch P, Rebolini E, Reining L, Romaniello P, Ruzsinszky A, Salahub DR, Scheffler M, Schwerdtfeger P, Staroverov VN, Sun J, Tellgren E, Tozer DJ, Trickey SB, Ullrich CA, Vela A, Vignale G, Wesolowski TA, Xu X, Yang W. DFT exchange: sharing perspectives on the workhorse of quantum chemistry and materials science. Phys Chem Chem Phys 2022; 24:28700-28781. [PMID: 36269074 PMCID: PMC9728646 DOI: 10.1039/d2cp02827a] [Citation(s) in RCA: 54] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Accepted: 08/09/2022] [Indexed: 12/13/2022]
Abstract
In this paper, the history, present status, and future of density-functional theory (DFT) is informally reviewed and discussed by 70 workers in the field, including molecular scientists, materials scientists, method developers and practitioners. The format of the paper is that of a roundtable discussion, in which the participants express and exchange views on DFT in the form of 302 individual contributions, formulated as responses to a preset list of 26 questions. Supported by a bibliography of 777 entries, the paper represents a broad snapshot of DFT, anno 2022.
Collapse
Affiliation(s)
- Andrew M. Teale
- School of Chemistry, University of Nottingham, University ParkNottinghamNG7 2RDUK
| | - Trygve Helgaker
- Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo, Norway.
| | - Andreas Savin
- Laboratoire de Chimie Théorique, CNRS and Sorbonne University, 4 Place Jussieu, CEDEX 05, 75252 Paris, France.
| | - Carlo Adamo
- PSL University, CNRS, ChimieParisTech-PSL, Institute of Chemistry for Health and Life Sciences, i-CLeHS, 11 rue P. et M. Curie, 75005 Paris, France.
| | - Bálint Aradi
- Bremen Center for Computational Materials Science, University of Bremen, P.O. Box 330440, D-28334 Bremen, Germany.
| | - Alexei V. Arbuznikov
- Technische Universität Berlin, Institut für Chemie, Theoretische Chemie/Quantenchemie, Sekr. C7Straße des 17. Juni 13510623Berlin
| | | | - Evert Jan Baerends
- Department of Chemistry and Pharmaceutical Sciences, Faculty of Science, Vrije Universiteit, De Boelelaan 1083, 1081HV Amsterdam, The Netherlands.
| | - Vincenzo Barone
- Scuola Normale Superiore, Piazza dei Cavalieri 7, 56125 Pisa, Italy.
| | - Patrizia Calaminici
- Departamento de Química, Centro de Investigación y de Estudios Avanzados (Cinvestav), CDMX, 07360, Mexico.
| | - Eric Cancès
- CERMICS, Ecole des Ponts and Inria Paris, 6 Avenue Blaise Pascal, 77455 Marne-la-Vallée, France.
| | - Emily A. Carter
- Department of Mechanical and Aerospace Engineering and the Andlinger Center for Energy and the Environment, Princeton UniversityPrincetonNJ 08544-5263USA
| | | | - Henry Chermette
- Institut Sciences Analytiques, Université Claude Bernard Lyon1, CNRS UMR 5280, 69622 Villeurbanne, France.
| | - Ilaria Ciofini
- PSL University, CNRS, ChimieParisTech-PSL, Institute of Chemistry for Health and Life Sciences, i-CLeHS, 11 rue P. et M. Curie, 75005 Paris, France.
| | - T. Daniel Crawford
- Department of Chemistry, Virginia TechBlacksburgVA 24061USA,Molecular Sciences Software InstituteBlacksburgVA 24060USA
| | - Frank De Proft
- Research Group of General Chemistry (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels, Belgium.
| | | | - Claudia Draxl
- Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, 12489 Berlin, Germany. .,Fritz-Haber-Institut der Max-Planck-Gesellschaft, 14195 Berlin, Germany
| | - Thomas Frauenheim
- Bremen Center for Computational Materials Science, University of Bremen, P.O. Box 330440, D-28334 Bremen, Germany. .,Beijing Computational Science Research Center (CSRC), 100193 Beijing, China.,Shenzhen JL Computational Science and Applied Research Institute, 518110 Shenzhen, China
| | - Emmanuel Fromager
- Laboratoire de Chimie Quantique, Institut de Chimie, CNRS/Université de Strasbourg, 4 rue Blaise Pascal, 67000 Strasbourg, France.
| | - Patricio Fuentealba
- Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile.
| | - Laura Gagliardi
- Department of Chemistry, Pritzker School of Molecular Engineering, The James Franck Institute, and Chicago Center for Theoretical Chemistry, The University of Chicago, Chicago, Illinois 60637, USA.
| | - Giulia Galli
- Pritzker School of Molecular Engineering and Department of Chemistry, The University of Chicago, Chicago, IL, USA.
| | - Jiali Gao
- Institute of Systems and Physical Biology, Shenzhen Bay Laboratory, Shenzhen 518055, China. .,Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA
| | - Paul Geerlings
- Research Group of General Chemistry (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels, Belgium.
| | - Nikitas Gidopoulos
- Department of Physics, Durham University, South Road, Durham DH1 3LE, UK.
| | - Peter M. W. Gill
- School of Chemistry, University of SydneyCamperdown NSW 2006Australia
| | - Paola Gori-Giorgi
- Department of Chemistry and Pharmaceutical Sciences, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Faculty of Science, Vrije Universiteit, De Boelelaan 1083, 1081HV Amsterdam, The Netherlands.
| | - Andreas Görling
- Chair of Theoretical Chemistry, University of Erlangen-Nuremberg, Egerlandstrasse 3, 91058 Erlangen, Germany.
| | - Tim Gould
- Qld Micro- and Nanotechnology Centre, Griffith University, Gold Coast, Qld 4222, Australia.
| | - Stefan Grimme
- Mulliken Center for Theoretical Chemistry, University of Bonn, Beringstrasse 4, 53115 Bonn, Germany.
| | - Oleg Gritsenko
- Department of Chemistry and Pharmaceutical Sciences, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Faculty of Science, Vrije Universiteit, De Boelelaan 1083, 1081HV Amsterdam, The Netherlands.
| | - Hans Jørgen Aagaard Jensen
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, DK-5230 Odense M, Denmark.
| | - Erin R. Johnson
- Department of Chemistry, Dalhousie UniversityHalifaxNova ScotiaB3H 4R2Canada
| | - Robert O. Jones
- Peter Grünberg Institut PGI-1, Forschungszentrum Jülich52425 JülichGermany
| | - Martin Kaupp
- Technische Universität Berlin, Institut für Chemie, Theoretische Chemie/Quantenchemie, Sekr. C7, Straße des 17. Juni 135, 10623, Berlin.
| | - Andreas M. Köster
- Departamento de Química, Centro de Investigación y de Estudios Avanzados (Cinvestav)CDMX07360Mexico
| | - Leeor Kronik
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovoth, 76100, Israel.
| | - Anna I. Krylov
- Department of Chemistry, University of Southern CaliforniaLos AngelesCalifornia 90089USA
| | - Simen Kvaal
- Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo, Norway.
| | - Andre Laestadius
- Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo, Norway.
| | - Mel Levy
- Department of Chemistry, Tulane University, New Orleans, Louisiana, 70118, USA.
| | - Mathieu Lewin
- CNRS & CEREMADE, Université Paris-Dauphine, PSL Research University, Place de Lattre de Tassigny, 75016 Paris, France.
| | - Shubin Liu
- Research Computing Center, University of North Carolina, Chapel Hill, NC 27599-3420, USA. .,Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599-3290, USA
| | - Pierre-François Loos
- Laboratoire de Chimie et Physique Quantiques (UMR 5626), Université de Toulouse, CNRS, UPS, France.
| | - Neepa T. Maitra
- Department of Physics, Rutgers University at Newark101 Warren StreetNewarkNJ 07102USA
| | - Frank Neese
- Max Planck Institut für Kohlenforschung, Kaiser Wilhelm Platz 1, D-45470 Mülheim an der Ruhr, Germany.
| | - John P. Perdew
- Departments of Physics and Chemistry, Temple UniversityPhiladelphiaPA 19122USA
| | - Katarzyna Pernal
- Institute of Physics, Lodz University of Technology, ul. Wolczanska 219, 90-924 Lodz, Poland.
| | - Pascal Pernot
- Institut de Chimie Physique, UMR8000, CNRS and Université Paris-Saclay, Bât. 349, Campus d'Orsay, 91405 Orsay, France.
| | - Piotr Piecuch
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA. .,Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - Elisa Rebolini
- Institut Laue Langevin, 71 avenue des Martyrs, 38000 Grenoble, France.
| | - Lucia Reining
- Laboratoire des Solides Irradiés, CNRS, CEA/DRF/IRAMIS, École Polytechnique, Institut Polytechnique de Paris, F-91120 Palaiseau, France. .,European Theoretical Spectroscopy Facility
| | - Pina Romaniello
- Laboratoire de Physique Théorique (UMR 5152), Université de Toulouse, CNRS, UPS, France.
| | - Adrienn Ruzsinszky
- Department of Physics, Temple University, Philadelphia, Pennsylvania 19122, USA.
| | - Dennis R. Salahub
- Department of Chemistry, Department of Physics and Astronomy, CMS – Centre for Molecular Simulation, IQST – Institute for Quantum Science and Technology, Quantum Alberta, University of Calgary2500 University Drive NWCalgaryAlbertaT2N 1N4Canada
| | - Matthias Scheffler
- The NOMAD Laboratory at the FHI of the Max-Planck-Gesellschaft and IRIS-Adlershof of the Humboldt-Universität zu Berlin, Faradayweg 4-6, D-14195, Germany.
| | - Peter Schwerdtfeger
- Centre for Theoretical Chemistry and Physics, The New Zealand Institute for Advanced Study, Massey University Auckland, 0632 Auckland, New Zealand.
| | - Viktor N. Staroverov
- Department of Chemistry, The University of Western OntarioLondonOntario N6A 5B7Canada
| | - Jianwei Sun
- Department of Physics and Engineering Physics, Tulane University, New Orleans, LA 70118, USA.
| | - Erik Tellgren
- Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo, Norway.
| | - David J. Tozer
- Department of Chemistry, Durham UniversitySouth RoadDurhamDH1 3LEUK
| | - Samuel B. Trickey
- Quantum Theory Project, Deptartment of Physics, University of FloridaGainesvilleFL 32611USA
| | - Carsten A. Ullrich
- Department of Physics and Astronomy, University of MissouriColumbiaMO 65211USA
| | - Alberto Vela
- Departamento de Química, Centro de Investigación y de Estudios Avanzados (Cinvestav), CDMX, 07360, Mexico.
| | - Giovanni Vignale
- Department of Physics, University of Missouri, Columbia, MO 65203, USA.
| | - Tomasz A. Wesolowski
- Department of Physical Chemistry, Université de Genève30 Quai Ernest-Ansermet1211 GenèveSwitzerland
| | - Xin Xu
- Shanghai Key Laboratory of Molecular Catalysis and Innovation Materials, Collaborative Innovation Centre of Chemistry for Energy Materials, MOE Laboratory for Computational Physical Science, Department of Chemistry, Fudan University, Shanghai 200433, China.
| | - Weitao Yang
- Department of Chemistry and Physics, Duke University, Durham, NC 27516, USA.
| |
Collapse
|
4
|
Ji L, Riese S, Schmiedel A, Holzapfel M, Fest M, Nitsch J, Curchod BFE, Friedrich A, Wu L, Al Mamari HH, Hammer S, Pflaum J, Fox MA, Tozer DJ, Finze M, Lambert C, Marder TB. Thermodynamic equilibrium between locally excited and charge-transfer states through thermally activated charge transfer in 1-(pyren-2'-yl)- o-carborane. Chem Sci 2022; 13:5205-5219. [PMID: 35655553 PMCID: PMC9093154 DOI: 10.1039/d1sc06867a] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 03/24/2022] [Indexed: 02/02/2023] Open
Abstract
Reversible conversion between excited-states plays an important role in many photophysical phenomena. Using 1-(pyren-2'-yl)-o-carborane as a model, we studied the photoinduced reversible charge-transfer (CT) process and the thermodynamic equilibrium between the locally-excited (LE) state and CT state, by combining steady state, time-resolved, and temperature-dependent fluorescence spectroscopy, fs- and ns-transient absorption, and DFT and LR-TDDFT calculations. Our results show that the energy gaps and energy barriers between the LE, CT, and a non-emissive 'mixed' state of 1-(pyren-2'-yl)-o-carborane are very small, and all three excited states are accessible at room temperature. The internal-conversion and reverse internal-conversion between LE and CT states are significantly faster than the radiative decay, and the two states have the same lifetimes and are in thermodynamic equilibrium.
Collapse
Affiliation(s)
- Lei Ji
- Frontiers Science Center for Flexible Electronics, Xi'an Institute of Flexible Electronics (IFE), Northwestern Polytechnical University 127 West Youyi Road Xi'an Shaanxi China .,Institut für Anorganische Chemie and Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Stefan Riese
- Institut für Organische Chemie, Julius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Alexander Schmiedel
- Institut für Organische Chemie, Julius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Marco Holzapfel
- Institut für Organische Chemie, Julius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Maximillian Fest
- Institut für Anorganische Chemie and Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Jörn Nitsch
- Institut für Anorganische Chemie and Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Basile F E Curchod
- Department of Chemistry, University of Durham South Road Durham DH1 3LE UK
| | - Alexandra Friedrich
- Institut für Anorganische Chemie and Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Lin Wu
- Frontiers Science Center for Flexible Electronics, Xi'an Institute of Flexible Electronics (IFE), Northwestern Polytechnical University 127 West Youyi Road Xi'an Shaanxi China
| | - Hamad H Al Mamari
- Institut für Anorganische Chemie and Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany .,Department of Chemistry, College of Science, Sultan Qaboos University PO Box 36, Al Khoudh 123 Muscat Sultanate of Oman
| | - Sebastian Hammer
- Experimentelle Physik VI, Julius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Jens Pflaum
- Experimentelle Physik VI, Julius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Mark A Fox
- Department of Chemistry, University of Durham South Road Durham DH1 3LE UK
| | - David J Tozer
- Department of Chemistry, University of Durham South Road Durham DH1 3LE UK
| | - Maik Finze
- Institut für Anorganische Chemie and Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Christoph Lambert
- Institut für Organische Chemie, Julius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Todd B Marder
- Institut für Anorganische Chemie and Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| |
Collapse
|
5
|
Abstract
In direct energy Kohn-Sham (DEKS) theory, the density functional theory electronic energy equals the sum of occupied orbital energies, obtained from Kohn-Sham-like orbital equations involving a shifted Hartree exchange-correlation potential, which must be approximated. In the present study, the Fermi-Amaldi term is incorporated into approximate DEKS calculations, introducing the required -1/r contribution to the exchange-correlation component of the shifted potential in asymptotic regions. It also provides a mechanism for eliminating one-electron self-interaction error, and it introduces a nonzero exchange-correlation component of the shift in the potential that is of appropriate magnitude. The resulting electronic energies are very sensitive to the methodologies considered, whereas the highest occupied molecular orbital energies and exchange-correlation potentials are much less sensitive and are similar to those obtained from DEKS calculations using a conventional exchange-correlation functional.
Collapse
Affiliation(s)
- Daisy J Dillon
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, U.K
| | - David J Tozer
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, U.K
| |
Collapse
|
6
|
Mensa-Bonsu G, Lietard A, Tozer DJ, Verlet JRR. Low energy electron impact resonances of anthracene probed by 2D photoelectron imaging of its radical anion. J Chem Phys 2020; 152:174303. [PMID: 32384861 DOI: 10.1063/5.0007470] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Electron-molecule resonances of anthracene were probed by 2D photoelectron imaging of the corresponding radical anion up to 3.7 eV in the continuum. A number of resonances were observed in both the photoelectron spectra and angular distributions, and most resonances showed clear autodetachment dynamics. The resonances were assigned using density functional theory calculations and are consistent with the available literature. Competition between direct and autodetachment, as well as signatures of internal conversion between resonances, was observed for some resonances. For the 12B2g resonance, a small fraction of population recovers the ground electronic state as evidenced by thermionic emission. Recovery of the ground electronic state offers a route of producing anions in an electron-molecule reaction; however, the energy at which this occurs suggests that anthracene anions cannot be formed in the interstellar medium by electron capture through this resonance.
Collapse
Affiliation(s)
- Golda Mensa-Bonsu
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - Aude Lietard
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - David J Tozer
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - Jan R R Verlet
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| |
Collapse
|
7
|
Abstract
The photoelectron spectra of para-benzoquinone radical cluster anions, (pBQ)n - (n = 2-4), taken at hv = 4.00 eV are presented and compared with the photoelectron spectrum of the monomer (n = 1). For all clusters, a direct detachment peak can be identified, and the incremental increase in the vertical detachment energy of ∼0.4 eV n-1 predominantly reflects the increase in cohesion energy as the cluster size increases. For all clusters, excitation also leads to low energy electrons that are produced by thermionic emission from ground electronic state anionic species, indicating that resonances are excited at this photon energy. For n = 3 and 4, photoelectron features at lower binding energy are observed which can be assigned to photodetachment from pBQ- for n = 3 and both pBQ- and (pBQ)2 - for n = 4. These observations indicate that the cluster dissociates on the time scale of the laser pulse (∼5 ns). The present results are discussed in the context of related quinone cluster anions.
Collapse
Affiliation(s)
- Golda Mensa-Bonsu
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - Mark R Wilson
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - David J Tozer
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - Jan R R Verlet
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| |
Collapse
|
8
|
Mensa-Bonsu G, Tozer DJ, Verlet JRR. Photoelectron spectroscopic study of I -·ICF 3: a frontside attack S N2 pre-reaction complex. Phys Chem Chem Phys 2019; 21:13977-13985. [PMID: 30534728 DOI: 10.1039/c8cp06593d] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photodetachment and 2D photoelectron spectra of the mass-selected I-·CF3I complex are presented together with electronic structure calculations. Calculations show that the I- is located at the iodine side of CF3I. Vertical and adiabatic detachment energies were measured at 4.03 and approximately 3.8 eV, respectively. The photoelectron spectra and molecular orbitals show a significant covalent bonding character in the cluster. The presence of electronic excited states is observed. Below threshold, iodide is generated which can be assigned to the photoexcitation of degenerate charge-transfer bands from the off-axis p-orbitals localised on iodide. Near the onset of two spin-orbit thresholds, bright excited states are seen in the experiment and calculations. Excitation of these leads to the formation of slow electrons. The spectroscopy of I-·CF3I is compared to the well-studied I-·CH3I cluster, a pre-reaction complex in the text-book I- + CH3I SN2 reaction. Despite the reversed stereodynamics (i.e. inversion of the CX3 between X = H and F) of the SN2 reaction, striking similarities are seen. Both complexes possess charge transfer excited states near their respective vertical detachment energies and exhibit vibrational structure in their photoelectron spectra. The strong binding is consistent with observations in crossed molecular beam studies and molecular dynamics simulations that suggest that iodine as a leaving group in an SN2 reaction affects the reaction dynamics.
Collapse
|
9
|
Abstract
A simple density functional theory (DFT) scheme is proposed for estimating negative vertical electron affinities of neutral systems, based on a consideration of the integer discontinuity and density scaling homogeneity. The key feature is the derivation of two system-dependent exchange-correlation functionals, one appropriate for the electron deficient side of the integer and one appropriate for the electron abundant side. The electron affinity is evaluated as a linear combination of frontier orbital energies from self-consistent Kohn-Sham calculations on the neutral system using these functionals. For two assessments comprising a total of 43 molecules, the scheme provides electron affinities that are in good agreement with experimental values and which are an improvement over those from the DFT method of Tozer and De Proft [ J. Phys. Chem. A 2005 , 109 , 8923 ]. The scheme is trivial to implement in any Kohn-Sham program, and the computational cost is that of a series of generalized gradient approximation Kohn-Sham calculations. More generally, the study provides a prescription for performing low-cost, self-consistent Kohn-Sham calculations that yield frontier orbital energies that approximately satisfy the appropriate Koopmans conditions, without the need for exact exchange.
Collapse
Affiliation(s)
| | - David J Tozer
- Department of Chemistry , Durham University , South Road , Durham , DH1 3LE U.K
| |
Collapse
|
10
|
|
11
|
Sharpe DJ, Levy M, Tozer DJ. Approximating the Shifted Hartree-Exchange-Correlation Potential in Direct Energy Kohn-Sham Theory. J Chem Theory Comput 2018; 14:684-692. [PMID: 29298061 DOI: 10.1021/acs.jctc.7b01060] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Levy and Zahariev [Phys. Rev. Lett. 113 113002 (2014)] have proposed a new approach for performing density functional theory calculations, termed direct energy Kohn-Sham (DEKS) theory. In this approach, the electronic energy equals the sum of orbital energies, obtained from Kohn-Sham-like orbital equations involving a shifted Hartree-exchange-correlation potential, which must be approximated. In the present study, density scaling homogeneity considerations are used to facilitate DEKS calculations on a series of atoms and molecules, leading to three nonlocal approximations to the shifted potential. The first two rely on preliminary Kohn-Sham calculations using a standard generalized gradient approximation (GGA) exchange-correlation functional and the results illustrate the benefit of describing the dominant Hartree component of the shift exactly. A uniform electron gas analysis is used to eliminate the need for these preliminary Kohn-Sham calculations, leading to a potential with an unconventional form that yields encouraging results, providing strong motivation for further research in DEKS theory.
Collapse
Affiliation(s)
- Daniel J Sharpe
- Department of Chemistry, Durham University , South Road, Durham, DH1 3LE U.K
| | - Mel Levy
- Department of Chemistry, Duke University , Durham, North Carolina 27708 United States.,Department of Physics, North Carolina A&T State University , Greensboro, North Carolina 27411 United States.,Department of Chemistry and Quantum Theory Group, Tulane University , New Orleans, Louisiana 70118 United States
| | - David J Tozer
- Department of Chemistry, Durham University , South Road, Durham, DH1 3LE U.K
| |
Collapse
|
12
|
Gledhill JD, De Proft F, Tozer DJ. Range-Separation Parameter in Tuned Exchange-Correlation Functionals: Successive Ionizations and the Fukui Function. J Chem Theory Comput 2016; 12:4879-4884. [PMID: 27622316 DOI: 10.1021/acs.jctc.6b00709] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The range-separation parameter in tuned, range-separated exchange-correlation functionals is investigated in two contexts. First, the system dependence of the parameter is investigated for a series of systems obtained by successively ionizing a single species, paying particular attention to the degree of linearity in the energy versus electron number curve. The parameter exhibits significant system dependence and, therefore, achieving near-linearity in one segment of the curve leads to strong nonlinearity in other segments. This provides a challenging test case for the development of new functionals designed to overcome the known problems of this class of functional. Next, the study considers whether a range-separation parameter tuned to a Koopmans energy condition is also applicable for the analogous density condition. This is tested by comparing two formulations of the Fukui function of conceptual density functional theory, for three representative systems. Both formulations yield the same general features and are not highly sensitive to the range-separation parameter. However, the agreement between the two is near-optimal when the energy-tuned parameter is used, indicating that this parameter is applicable for the analogous density condition.
Collapse
Affiliation(s)
- Jonathan D Gledhill
- Department of Chemistry, Durham University , South Road, Durham DH1 3LE, United Kingdom
| | - Frank De Proft
- Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB) , Pleinlaan 2, 1050 Brussels, Belgium
| | - David J Tozer
- Department of Chemistry, Durham University , South Road, Durham DH1 3LE, United Kingdom
| |
Collapse
|
13
|
Affiliation(s)
- Michael J. G. Peach
- Department
of Chemistry, Lancaster University, Lancaster LA1 4YB, United Kingdom
| | - Andrew M. Teale
- School
of Chemistry, University of Nottingham, Nottingham NG7 2RD, United Kingdom
- Department
of Chemistry, Centre for Theoretical and Computational Chemistry, University of Oslo, P.O.
Box 1033, Blindern, Oslo N-0315, Norway
| | - Trygve Helgaker
- Department
of Chemistry, Centre for Theoretical and Computational Chemistry, University of Oslo, P.O.
Box 1033, Blindern, Oslo N-0315, Norway
| | - David J. Tozer
- Department
of Chemistry, Durham University, South Road, Durham DH1 3LE, United Kingdom
| |
Collapse
|
14
|
Helgaker T, Knowles PJ, Lee TJ, Rice JE, Tozer DJ. Foreword. Mol Phys 2015. [DOI: 10.1080/00268976.2015.1047162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
15
|
Gledhill JD, Tozer DJ. System-dependent exchange–correlation functional with exact asymptotic potential and εHOMO ≈ − I. J Chem Phys 2015; 143:024104. [DOI: 10.1063/1.4926397] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Jonathan D. Gledhill
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, United Kingdom
| | - David J. Tozer
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, United Kingdom
| |
Collapse
|
16
|
Affiliation(s)
- David J Tozer
- Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, UK
| | | |
Collapse
|
17
|
Teale AM, De Proft F, Geerlings P, Tozer DJ. Atomic electron affinities and the role of symmetry between electron addition and subtraction in a corrected Koopmans approach. Phys Chem Chem Phys 2015; 16:14420-34. [PMID: 24406854 DOI: 10.1039/c3cp54528h] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The essential aspects of zero-temperature grand-canonical ensemble density-functional theory are reviewed in the context of spin-density-functional theory and are used to highlight the assumption of symmetry between electron addition and subtraction that underlies the corrected Koopmans approach of Tozer and De Proft (TDP) for computing electron affinities. The issue of symmetry is then investigated in a systematic study of atomic electron affinities, comparing TDP affinities with those from a conventional Koopmans evaluation and electronic energy differences. Although it cannot compete with affinities determined from energy differences, the TDP expression yields results that are a significant improvement over those from the conventional Koopmans expression. Key insight into the results from both expressions is provided by an analysis of plots of the electronic energy as a function of the number of electrons, which highlight the extent of symmetry between addition and subtraction. The accuracy of the TDP affinities is closely related to the nature of the orbitals involved in the electron addition and subtraction, being particularly poor in cases where there is a change in principal quantum number, but relatively accurate within a single manifold of orbitals. The analysis is then extended to a consideration of the ground state Mulliken electronegativity and chemical hardness. The findings further emphasize the key role of symmetry in determining the quality of the results.
Collapse
Affiliation(s)
- A M Teale
- School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
| | | | | | | |
Collapse
|
18
|
Cheng CY, Ryley MS, Peach MJ, Tozer DJ, Helgaker T, Teale AM. Molecular properties in the Tamm–Dancoff approximation: indirect nuclear spin–spin coupling constants. Mol Phys 2015. [DOI: 10.1080/00268976.2015.1024182] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Chi Y. Cheng
- School of Chemistry, University of Nottingham, Nottingham, UK
| | | | | | | | - Trygve Helgaker
- Department of Chemistry, Centre for Theoretical and Computational Chemistry, University of Oslo, Oslo, Norway
| | - Andrew M. Teale
- School of Chemistry, University of Nottingham, Nottingham, UK
- Department of Chemistry, Centre for Theoretical and Computational Chemistry, University of Oslo, Oslo, Norway
| |
Collapse
|
19
|
Affiliation(s)
- Alex Borgoo
- Department
of Chemistry, Centre for Theoretical and Computational Chemistry, University of Oslo, P.O.
Box 1033, Blindern, Oslo N-0315, Norway
| | - James A. Green
- Department
of Chemistry, Durham University, South Road, Durham DH1 3LE, U.K
| | - David J. Tozer
- Department
of Chemistry, Durham University, South Road, Durham DH1 3LE, U.K
| |
Collapse
|
20
|
Abstract
Two different density scaling approaches are compared and their prospects for use in functional development are reviewed.
Collapse
Affiliation(s)
- Alex Borgoo
- Department of Chemistry
- Centre for Theoretical and Computational Chemistry
- University of Oslo
- Oslo N-0315, Norway
| | - Andrew M. Teale
- Department of Chemistry
- Centre for Theoretical and Computational Chemistry
- University of Oslo
- Oslo N-0315, Norway
- School of Chemistry
| | | |
Collapse
|
21
|
|
22
|
Altmann DR, Button T, Schmierer K, Hunter K, Tozer DJ, Wheeler-Kingshott CA, Coles A, Miller DH. Sample sizes for lesion magnetisation transfer ratio outcomes in remyelination trials for multiple sclerosis. Mult Scler Relat Disord 2013; 3:237-43. [PMID: 25878011 DOI: 10.1016/j.msard.2013.09.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Revised: 09/06/2013] [Accepted: 09/16/2013] [Indexed: 11/26/2022]
Abstract
BACKGROUND Enhancing remyelination in MS might improve function and protect axons from future damage. Lesion magnetisation transfer ratio (MTR) is sensitive to myelin content, and may be a useful measure for trials evaluating potential remyelinating agents. OBJECTIVE Estimating sample sizes required for a parallel group, placebo-controlled trial in MS using change in mean MTR of all T2lesions as a primary outcome measure. METHODS The primary sample size calculation was derived from data from a natural history study of relapsing remitting MS (n=18). The MTR values observed in demyelinated and remyelinated lesions in an ex vivo study were used to estimate the effect of remyelination on lesion MTR. The ex vivo data were also used to independently calculate sample sizes in order to inform the robustness of the in vivo estimates. RESULTS Calculations suggest that 30% remyelination of T2 lesions could be detected with 80% power in 38 (95% confidence interval 12-96) patients per arm based on the in vivo data, and in 66 per arm based on the ex vivo data. CONCLUSION The sample sizes derived are in a range that makes MTR a feasible outcome measure for proof-of-concept trials of putative therapies achieving remyelination in MS lesions.
Collapse
Affiliation(s)
- D R Altmann
- Nuclear Magnetic Resonance (NMR) Research Unit, Queen Square Multiple Sclerosis Centre, UCL Institute of Neurology, London, UK; Medical Statistics Department, London School of Hygiene & Tropical Medicine (LSHTM), Keppel Street, London WC1E 7HT, UK.
| | - T Button
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK.
| | - K Schmierer
- Nuclear Magnetic Resonance (NMR) Research Unit, Queen Square Multiple Sclerosis Centre, UCL Institute of Neurology, London, UK; Blizard Institute, Centre for Neuroscience & Trauma, Barts and The London School of Medicine & Dentistry, London, UK.
| | - K Hunter
- Nuclear Magnetic Resonance (NMR) Research Unit, Queen Square Multiple Sclerosis Centre, UCL Institute of Neurology, London, UK.
| | - D J Tozer
- Nuclear Magnetic Resonance (NMR) Research Unit, Queen Square Multiple Sclerosis Centre, UCL Institute of Neurology, London, UK.
| | - C A Wheeler-Kingshott
- Nuclear Magnetic Resonance (NMR) Research Unit, Queen Square Multiple Sclerosis Centre, UCL Institute of Neurology, London, UK.
| | - A Coles
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK.
| | - D H Miller
- Nuclear Magnetic Resonance (NMR) Research Unit, Queen Square Multiple Sclerosis Centre, UCL Institute of Neurology, London, UK.
| |
Collapse
|
23
|
Gledhill JD, Peach MJG, Tozer DJ. Assessment of Tuning Methods for Enforcing Approximate Energy Linearity in Range-Separated Hybrid Functionals. J Chem Theory Comput 2013; 9:4414-20. [DOI: 10.1021/ct400592a] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Jonathan D. Gledhill
- Department
of Chemistry, Durham University, South Road, Durham, DH1
3LE, United Kingdom
| | - Michael J. G. Peach
- Department
of Chemistry, Faraday Building, Lancaster University, Lancaster, LA1 4YB, United Kingdom
| | - David J. Tozer
- Department
of Chemistry, Durham University, South Road, Durham, DH1
3LE, United Kingdom
| |
Collapse
|
24
|
Teale AM, Lutnæs OB, Helgaker T, Tozer DJ, Gauss J. Benchmarking density-functional theory calculations of NMR shielding constants and spin-rotation constants using accurate coupled-cluster calculations. J Chem Phys 2013; 138:024111. [PMID: 23320672 DOI: 10.1063/1.4773016] [Citation(s) in RCA: 131] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Accurate sets of benchmark nuclear-magnetic-resonance shielding constants and spin-rotation constants are calculated using coupled-cluster singles-doubles (CCSD) theory and coupled-cluster singles-doubles-perturbative-triples [CCSD(T)] theory, in a variety of basis sets consisting of (rotational) London atomic orbitals. The accuracy of the calculated coupled-cluster constants is established by a careful comparison with experimental data, taking into account zero-point vibrational corrections. Coupled-cluster basis-set convergence is analyzed and extrapolation techniques are employed to estimate basis-set-limit quantities, thereby establishing an accurate benchmark data set. Together with the set provided for rotational g-tensors and magnetizabilities in our previous work [O. B. Lutnæs, A. M. Teale, T. Helgaker, D. J. Tozer, K. Ruud, and J. Gauss, J. Chem. Phys. 131, 144104 (2009)], it provides a substantial source of consistently calculated high-accuracy data on second-order magnetic response properties. The utility of this benchmark data set is demonstrated by examining a wide variety of Kohn-Sham exchange-correlation functionals for the calculation of these properties. None of the existing approximate functionals provide an accuracy competitive with that provided by CCSD or CCSD(T) theory. The need for a careful consideration of vibrational effects is clearly illustrated. Finally, the pure coupled-cluster results are compared with the results of Kohn-Sham calculations constrained to give the same electronic density. Routes to future improvements are discussed in light of this comparison.
Collapse
Affiliation(s)
- Andrew M Teale
- Department of Chemistry, Centre for Theoretical and Computational Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo, Norway
| | | | | | | | | |
Collapse
|
25
|
Affiliation(s)
- Michael J.G. Peach
- a Department of Chemistry, Faraday Building , Durham University , Durham , UK
- b Department of Chemistry , Lancaster University , Lancaster , UK
| | - Neil Warner
- a Department of Chemistry, Faraday Building , Durham University , Durham , UK
| | - David J. Tozer
- a Department of Chemistry, Faraday Building , Durham University , Durham , UK
| |
Collapse
|
26
|
Affiliation(s)
- Alex Borgoo
- Department of Chemistry, Durham University, South Road,
Durham DH1 3LE, United Kingdom
| | - David J. Tozer
- Department of Chemistry, Durham University, South Road,
Durham DH1 3LE, United Kingdom
| |
Collapse
|
27
|
Abstract
MRI offers a number of opportunities to examine characteristics of tissue well below the spatial resolution of the imaging technique. The best known of these is diffusion imaging, which allows the production of images whose contrast reflects the ability of water molecules to move through the extravascular extracellular space. Less well-known, but increasingly important, is magnetisation transfer imaging, which produces contrast based on the ability of protons to move between the free water pool and local macromolecules. Both of these techniques offer unique information about the microscopic and molecular structure of tumour tissue. This article will briefly review the underlying theory and technical aspects associated with these imaging techniques.
Collapse
Affiliation(s)
- S J Price
- Academic Neurosurgery Division, Department of Clinical Neuroscience, UCL, London, UK.
| | | | | |
Collapse
|
28
|
Affiliation(s)
| | - David J. Tozer
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, U.K
| |
Collapse
|
29
|
Borgoo A, Tozer DJ. Negative Electron Affinities from DFT: Influence of Asymptotic Exchange-Correlation Potential and Effective Homogeneity under Density Scaling. J Phys Chem A 2012; 116:5497-500. [DOI: 10.1021/jp302801q] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Alex Borgoo
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, U.K
| | - David J. Tozer
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, U.K
| |
Collapse
|
30
|
Peach MJG, Griffiths DGJ, Tozer DJ. On the evaluation of the non-interacting kinetic energy in density functional theory. J Chem Phys 2012; 136:144101. [DOI: 10.1063/1.3700436] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
31
|
Borgoo A, Teale AM, Tozer DJ. Effective homogeneity of the exchange–correlation and non-interacting kinetic energy functionals under density scaling. J Chem Phys 2012; 136:034101. [DOI: 10.1063/1.3676722] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
|
32
|
Weber L, Eickhoff D, Marder TB, Fox MA, Low PJ, Dwyer AD, Tozer DJ, Schwedler S, Brockhinke A, Stammler HG, Neumann B. Experimental and Theoretical Studies on Organic D-π-A Systems Containing Three-Coordinate Boron Moieties as both π-Donor and π-Acceptor. Chemistry 2011; 18:1369-82. [DOI: 10.1002/chem.201102059] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Indexed: 11/07/2022]
|
33
|
Dwyer AD, Tozer DJ. Dispersion, static correlation, and delocalisation errors in density functional theory: An electrostatic theorem perspective. J Chem Phys 2011; 135:164110. [DOI: 10.1063/1.3653980] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
34
|
Abstract
Singlet and triplet vertical excitation energies from time-dependent density functional theory (TDDFT) can be affected in different ways by the inclusion of exact exchange in hybrid or Coulomb-attenuated/range-separated exchange-correlation functionals; in particular, triplet excitation energies can become significantly too low. To investigate these issues, the explicit dependence of excitation energies on exact exchange is quantified for four representative molecules, paying attention to the effect of constant, short-range, and long-range contributions. A stability analysis is used to verify that the problematic TDDFT triplet excitations can be understood in terms of the ground state triplet instability problem, and it is proposed that a Hartree-Fock stability analysis should be used to identify triplet excitations for which the presence of exact exchange in the TDDFT functional is undesirable. The use of the Tamm-Dancoff approximation (TDA) significantly improves the problematic triplet excitation energies, recovering the correct state ordering in benzoquinone; it also affects the corresponding singlet states, recovering the correct state ordering in naphthalene. The impressive performance of the TDA is maintained for a wide range of molecules across representative functionals.
Collapse
Affiliation(s)
- Michael J G Peach
- Department of Chemistry, Durham University , South Road, Durham, DH1 3LE United Kingdom
| | - Matthew J Williamson
- Department of Chemistry, Durham University , South Road, Durham, DH1 3LE United Kingdom
| | - David J Tozer
- Department of Chemistry, Durham University , South Road, Durham, DH1 3LE United Kingdom
| |
Collapse
|
35
|
Petzold A, Tozer DJ, Schmierer K. Axonal damage in the making: neurofilament phosphorylation, proton mobility and magnetisation transfer in multiple sclerosis normal appearing white matter. Exp Neurol 2011; 232:234-9. [PMID: 21958956 PMCID: PMC3277890 DOI: 10.1016/j.expneurol.2011.09.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Revised: 09/06/2011] [Accepted: 09/09/2011] [Indexed: 11/29/2022]
Abstract
Aims Multiple sclerosis (MS) leaves a signature on the phosphorylation and thus proton binding capacity of axonal neurofilament (Nf) proteins. The proton binding capacity in a tissue is the major determinant for exchange between bound and free protons and thus the magnetisation transfer ratio (MTR). This study investigated whether the MTR of non-lesional white matter (NLWM) was related to the brain tissue concentration of neurofilament phosphoforms. Methods Unfixed post-mortem brain slices of 12 MS patients were analysed using MTR, T1 at 1.5 T. Blocks containing NLWM were processed for embedding in paraffin and inspected microscopically. Adjacent tissue was microdissected, homogenised and specific protein levels were quantified by ELISA for the Nf heavy chain (NfH) phosphoforms, glial fibrillary acidic protein (GFAP), S100B and ferritin. Results Averaged hyperphosphorylated NfH (SMI34) but not phosphorylated NfH (SMI35) levels were different between individual patients NLWM. The concentration of hyperphosphorylated NfH-SMI34 correlated with T1 (R = 0.70, p = 0.0114) and — inversely — with MTR (R =−0.73, p = 0.0065). NfH-SMI35 was not correlated to any of the MR indices. Conclusions Post-translational modifications of axonal proteins such as phosphorylation of neurofilaments occur in NLWM and may precede demyelination. The resulting change of proton mobility influences MTR and T1. This permits the in vivo detection of these subtle tissue changes on a proteomic level in patients with MS.
Collapse
Affiliation(s)
- A Petzold
- UCL Institute of Neurology, Department of Neuroinflammation, Queen Square, London WC1N 3BG, UK.
| | | | | |
Collapse
|
36
|
Hayton T, Furby J, Smith KJ, Altmann DR, Brenner R, Chataway J, Hunter K, Tozer DJ, Miller DH, Kapoor R. Longitudinal changes in magnetisation transfer ratio in secondary progressive multiple sclerosis: data from a randomised placebo controlled trial of lamotrigine. J Neurol 2011; 259:505-14. [PMID: 21904901 DOI: 10.1007/s00415-011-6212-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2011] [Revised: 07/28/2011] [Accepted: 08/02/2011] [Indexed: 10/17/2022]
Abstract
Sodium blockade with lamotrigine is neuroprotective in animal models of central nervous system demyelination. This study evaluated the effect of lamotrigine on magnetisation transfer ratio (MTR), a putative magnetic resonance imaging measure of intact brain tissue, in a group of subjects with secondary progressive multiple sclerosis (MS). In addition, the utility of MTR measures for detecting change in clinically relevant pathology was evaluated. One hundred seventeen people attending the National Hospital for Neurology and Neurosurgery or the Royal Free Hospital, London, UK, were recruited into a double-blind, parallel-group trial. Subjects were randomly assigned by minimisation to receive lamotrigine (target dose 400 mg/day) or placebo for 2 years. Treating and assessing physicians and patients were masked to treatment allocation. Results of the primary endpoint, central cerebral volume, have been published elsewhere. Significant differences between the verum and placebo arms were seen in only two measures [normal appearing grey matter (NAGM) p = 0.036 and lesion peak height (PH) p = 0.004], and in both cases there was a greater reduction in MTR in the verum arm. Significant correlations were found of change in MS functional composite with all MTR measures except lesion and normal appearing white matter (NAWM) PH. However, the change in MTR measures over 2 years were small, with only NAGM mean (p = 0.001), lesion peak location (p = 0.11) and mean (p < 0.0001) changing significantly from baseline. These data did not show that lamotrigine was neuroprotective. The clinical correlation of MTR measures was consistent, but the responsiveness to change was limited.
Collapse
Affiliation(s)
- T Hayton
- Department of Neuroinflammation, UCL Institute of Neurology, Queen Square, London, WC1N 3BG, UK.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
37
|
Crawford AG, Dwyer AD, Liu Z, Steffen A, Beeby A, Pålsson LO, Tozer DJ, Marder TB. Experimental and Theoretical Studies of the Photophysical Properties of 2- and 2,7-Functionalized Pyrene Derivatives. J Am Chem Soc 2011; 133:13349-62. [DOI: 10.1021/ja2006862] [Citation(s) in RCA: 242] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Andrew G. Crawford
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, United Kingdom
| | - Austin D. Dwyer
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, United Kingdom
| | - Zhiqiang Liu
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, United Kingdom
- State Key Lab of Crystal Materials, Shandong University, 27 Shanda South Road, Jinan 250100, China
| | - Andreas Steffen
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, United Kingdom
| | - Andrew Beeby
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, United Kingdom
| | - Lars-Olof Pålsson
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, United Kingdom
| | - David J. Tozer
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, United Kingdom
| | - Todd B. Marder
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, United Kingdom
| |
Collapse
|
38
|
Hajgató B, De Proft F, Szieberth D, Tozer DJ, Deleuze MS, Geerlings P, Nyulászi L. Bonding in negative ions: the role of d orbitals in the heavy analogues of pyridine and furanradical anions. Phys Chem Chem Phys 2011; 13:1663-8. [DOI: 10.1039/c0cp01151g] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
|
39
|
Cárdenas C, Ayers P, De Proft F, Tozer DJ, Geerlings P. Should negative electron affinities be used for evaluating the chemical hardness? Phys Chem Chem Phys 2010; 13:2285-93. [PMID: 21113528 DOI: 10.1039/c0cp01785j] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Despite recent advances in computing negative electron affinities using density-functional theory, it is an open issue as to whether it is appropriate to use negative electron affinities, instead of zero electron affinity, to compute the chemical hardness of atoms and molecules with metastable anions. We seek to answer this question using the accepted empirical rules linking the chemical hardness to the atomic size and the polarizability; we also propose a new correlation with the C6 London dispersion coefficient. For chemical reactivity in the gas phase, it seems to make no difference whether negative, or zero, electron affinities are used for systems with metastable anions. For reactions in solution the evidence that is presently available is insufficient to establish a preference. In addressing this issue, we noted that electron affinity data from which atomic chemical hardness values are computed are out of date; an update to Pearson's classic 1988 table [Inorg. Chem., 1988, 27, 734-740] is thus provided.
Collapse
Affiliation(s)
- Carlos Cárdenas
- Departamento de Física, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Ñuñoa, Santiago, Chile.
| | | | | | | | | |
Collapse
|
40
|
Plötner J, Tozer DJ, Dreuw A. Dependence of Excited State Potential Energy Surfaces on the Spatial Overlap of the Kohn−Sham Orbitals and the Amount of Nonlocal Hartree−Fock Exchange in Time-Dependent Density Functional Theory. J Chem Theory Comput 2010; 6:2315-24. [DOI: 10.1021/ct1001973] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Jürgen Plötner
- Institute of Physical and Theoretical Chemistry, Goethe-University Frankfurt, Max von Laue-Strasse 7, 60438 Frankfurt, Germany, and Department of Chemistry, University of Durham, South Road, Durham DH1 3LE, United Kingdom
| | - David J. Tozer
- Institute of Physical and Theoretical Chemistry, Goethe-University Frankfurt, Max von Laue-Strasse 7, 60438 Frankfurt, Germany, and Department of Chemistry, University of Durham, South Road, Durham DH1 3LE, United Kingdom
| | - Andreas Dreuw
- Institute of Physical and Theoretical Chemistry, Goethe-University Frankfurt, Max von Laue-Strasse 7, 60438 Frankfurt, Germany, and Department of Chemistry, University of Durham, South Road, Durham DH1 3LE, United Kingdom
| |
Collapse
|
41
|
Peach MJG, Kattirtzi JA, Teale AM, Tozer DJ. Shielding Constants and Chemical Shifts in DFT: Influence of Optimized Effective Potential and Coulomb-Attenuation. J Phys Chem A 2010; 114:7179-86. [DOI: 10.1021/jp102465x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Michael J. G. Peach
- Institut für Theoretische Physik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany, Department of Chemistry, University of Durham, Durham DH1 3LE, United Kingdom, and Department of Chemistry, Centre for Theoretical and Computational Chemistry, University of Oslo, P.O. Box 1033, Blindern, N-0315 Oslo, Norway
| | - John A. Kattirtzi
- Institut für Theoretische Physik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany, Department of Chemistry, University of Durham, Durham DH1 3LE, United Kingdom, and Department of Chemistry, Centre for Theoretical and Computational Chemistry, University of Oslo, P.O. Box 1033, Blindern, N-0315 Oslo, Norway
| | - Andrew M. Teale
- Institut für Theoretische Physik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany, Department of Chemistry, University of Durham, Durham DH1 3LE, United Kingdom, and Department of Chemistry, Centre for Theoretical and Computational Chemistry, University of Oslo, P.O. Box 1033, Blindern, N-0315 Oslo, Norway
| | - David J. Tozer
- Institut für Theoretische Physik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany, Department of Chemistry, University of Durham, Durham DH1 3LE, United Kingdom, and Department of Chemistry, Centre for Theoretical and Computational Chemistry, University of Oslo, P.O. Box 1033, Blindern, N-0315 Oslo, Norway
| |
Collapse
|
42
|
Dwyer AD, Tozer DJ. Effect of chemical change on TDDFT accuracy: orbital overlap perspective of the hydrogenation of retinal. Phys Chem Chem Phys 2010; 12:2816-8. [DOI: 10.1039/c002428g] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
43
|
Lutnæs OB, Teale AM, Helgaker T, Tozer DJ, Ruud K, Gauss J. Benchmarking density-functional-theory calculations of rotational g tensors and magnetizabilities using accurate coupled-cluster calculations. J Chem Phys 2009; 131:144104. [DOI: 10.1063/1.3242081] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
44
|
Nasomjai P, Reed DW, Tozer DJ, Peach MJG, Slawin AMZ, Covello PS, O'Hagan D. Mechanistic Insights into the Cytochrome P450-Mediated Oxidation and Rearrangement of Littorine in Tropane Alkaloid Biosynthesis. Chembiochem 2009; 10:2382-93. [DOI: 10.1002/cbic.200900318] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
45
|
Fisniku LK, Altmann DR, Cercignani M, Tozer DJ, Chard DT, Jackson JS, Miszkiel KA, Schmierer K, Thompson AJ, Miller DH. Magnetization transfer ratio abnormalities reflect clinically relevant grey matter damage in multiple sclerosis. Mult Scler 2009; 15:668-77. [PMID: 19435751 DOI: 10.1177/1352458509103715] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
BACKGROUND In multiple sclerosis, grey matter (GM) damage appears more clinically relevant than either white matter damage or lesion load. OBJECTIVE We investigated if normal-appearing white matter (NAWM) and grey matter tissue changes assessed by magnetization transfer ratio were associated with long-term disability. METHODS Sixty-nine people were assessed 20 years after presentation with a clinically isolated syndrome (CIS) [28 still CIS, 31 relapsing-remitting multiple sclerosis, 10 secondary progressive multiple sclerosis], along with 19 healthy subjects. Mean magnetization transfer ratio, peak height (PH) and peak location of the normalized magnetization transfer ratio histograms were determined in NAWM and grey matter, as well as, white matter and GM Fraction (GMF) and T(2)-weighted lesion load. RESULTS Median expanded disability status scale for multiple sclerosis patients was 2.5 (range 1-8). GM-PH, and less so, NAWM mean and peak location, were lower in multiple sclerosis patients (P = 0.009) versus controls, relapsing-remitting multiple sclerosis versus CIS (P = 0.008) and secondary progressive multiple sclerosis versus relapsing-remitting multiple sclerosis (P = 0.002). GM-PH (as well as GMF) correlated with expanded disability status scale (r(s) = -0.49; P = 0.001) and multiple sclerosis functional score (r(s) = 0.51; P = 0.001). GM-PH independently predicted disability with similar strength to the associations of GMF with clinical measures. CONCLUSION Grey matter damage was related to long-term disability in multiple sclerosis cohort with a relatively low median expanded disability status scale. Markers of intrinsic grey matter damage (magnetization transfer ratio) and tissue loss offer clinically relevant information in multiple sclerosis.
Collapse
Affiliation(s)
- L K Fisniku
- NMR Research Unit, Department of Neuroinflammation, Institute of Neurology, University College London, London, UK.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
46
|
Hayton T, Furby J, Smith KJ, Altmann DR, Brenner R, Chataway J, Hughes RAC, Hunter K, Tozer DJ, Miller DH, Kapoor R. Grey matter magnetization transfer ratio independently correlates with neurological deficit in secondary progressive multiple sclerosis. J Neurol 2009; 256:427-35. [PMID: 19271108 DOI: 10.1007/s00415-009-0110-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2008] [Revised: 09/03/2008] [Accepted: 09/24/2008] [Indexed: 10/21/2022]
Abstract
Although there is substantial brain grey matter pathology in secondary progressive multiple sclerosis (MS), there has been limited investigation of its contribution to disability.This study investigated the correlation of magnetization transfer ratio (MTR) measures taken from brain grey matter, normal appearing white matter (NAWM) and lesions with neurological deficit and disability in 113 people with secondary progressive MS. In order to adjust for the potential effects of focal white matter lesions and global brain atrophy, T2 lesion volume and normalized brain volume (NBV) were also calculated for each subject. Clinical measures included the expanded disability status scale (EDSS) and the multiple sclerosis functional composite (MSFC) scores. Linear regression analysis was used to assess the age- and gender-adjusted correlation of MTR histogram mean, peak height and peak location with the MSFC and individual component measures. Logistic regression analysis was used to determine whether imaging measures could be used to predict if subjects were in the higher disability group (EDSS > or = 6.5).Significant correlations were detected between MSFC composite and mean MTR in (i) normal appearing white matter (NAWM; r = 0.327, p < 0.0001), (ii) grey matter (r = 0.460, p < 0.0001) and (iii) lesions (r = 0.394, p < 0.0001). Although NBV and T2 lesion volume correlated significantly with MSFC, grey matter histogram mean emerged as the best predictor of MSFC score. None of the MRI measures significantly predicted higher EDSS.These results suggest that brain grey matter pathology plays an important role in determining neurological impairment. The apparent paucity of correlation between MRI measures and EDSS is likely to represent the relative insensitivity of the latter measure in this study group.
Collapse
Affiliation(s)
- T Hayton
- Dept. of Neuroinflammation, Institute of Neurology, Queen Square, London, WC1N 3BG, UK.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
47
|
Peach MJG, Le Sueur CR, Ruud K, Guillaume M, Tozer DJ. TDDFT diagnostic testing and functional assessment for triazene chromophores. Phys Chem Chem Phys 2009; 11:4465-70. [PMID: 19475164 DOI: 10.1039/b822941d] [Citation(s) in RCA: 131] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A simple diagnostic test based on orbital overlap [M. J. G. Peach et al., J. Chem. Phys., 2008, 128, 044118] may be used to help judge the reliability of excitation energies in time-dependent density functional theory (TDDFT) when using generalized gradient approximation (GGA) and hybrid functionals. Orbital plots are used to illustrate the test for a model tripeptide and for 4-(N,N-dimethylamino)benzonitrile, which are representative of systems containing low- and high-overlap charge-transfer excitations. The scheme is then applied to a series of triazene chromophores in solvent, highlighting the relationship between overlap and oscillator strength and its implications for theoretical absorption spectra. No low-overlap excitations are observed with a hybrid functional; a single one is identified using a GGA. To assess the diagnostic test and to judge functional performance, gas phase triazene TDDFT excitations are compared with correlated ab initio values. The diagnostic test correctly identifies two low-overlap problematic GGA excitations. However, it does not identify another problematic excitation where the electron is excited to a spatially extended orbital, which necessarily has reasonable overlap with the occupied orbital; an improved diagnostic quantity is required for such cases. The best agreement between TDDFT and correlated ab initio excitations is obtained using a Coulomb-attenuated functional; the errors are significantly smaller than from the GGA and hybrid functionals. The study provides further support for the high quality excitations from Coulomb-attenuated functionals, negating the need for diagnostic tests.
Collapse
Affiliation(s)
- Michael J G Peach
- Department of Chemistry, University of Durham, South Road, Durham, UK DH1 3LE
| | | | | | | | | |
Collapse
|
48
|
Wiggins P, Williams JAG, Tozer DJ. Excited state surfaces in density functional theory: A new twist on an old problem. J Chem Phys 2009; 131:091101. [DOI: 10.1063/1.3222641] [Citation(s) in RCA: 151] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
49
|
Besley NA, Peach MJG, Tozer DJ. Time-dependent density functional theory calculations of near-edge X-ray absorption fine structure with short-range corrected functionals. Phys Chem Chem Phys 2009; 11:10350-8. [DOI: 10.1039/b912718f] [Citation(s) in RCA: 142] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
50
|
Borgoo A, Tozer DJ, Geerlings P, De Proft F. Confinement effects on excitation energies and regioselectivity as probed by the Fukui function and the molecular electrostatic potential. Phys Chem Chem Phys 2009; 11:2862-8. [DOI: 10.1039/b820114e] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|