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Martinez-Garcia A, de Ara T, Pastor-Amat L, Untiedt C, Lombardi EB, Dednam W, Sabater C. Unraveling the Interplay between Quantum Transport and Geometrical Conformations in Monocyclic Hydrocarbons' Molecular Junctions. J Phys Chem C Nanomater Interfaces 2023; 127:23303-23311. [PMID: 38352239 PMCID: PMC10861133 DOI: 10.1021/acs.jpcc.3c05393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 11/07/2023] [Accepted: 11/15/2023] [Indexed: 02/16/2024]
Abstract
In the field of molecular electronics, especially in quantum transport experiments, determining the geometrical configurations of a single molecule trapped between two electrodes can be challenging. To address this challenge, we employed a combination of molecular dynamics (MD) simulations and electronic transport calculations based on density functional theory to determine the molecular orientation in our break-junction experiments under ambient conditions. The molecules used in this study are common solvents used in molecular electronics, such as benzene, toluene (aromatic), and cyclohexane (aliphatic). Furthermore, we introduced a novel criterion based on the normal vector of the surface formed by the cavity of these ring-shaped monocyclic hydrocarbon molecules to clearly define the orientation of the molecules with respect to the electrodes. By comparing the results obtained through MD simulations and density functional theory with experimental data, we observed that both are in good agreement. This agreement helps us to uncover the different geometrical configurations that these molecules adopt in break-junction experiments. This approach can significantly improve our understanding of molecular electronics, especially when using more complex cyclic hydrocarbons.
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Affiliation(s)
- A. Martinez-Garcia
- Departamento
de Física Aplicada and Instituto Universitario de Materiales
de Alicante (IUMA), Universidad de Alicante, Campus de San Vicente del Raspeig, Alicante E-03690, Spain
| | - T. de Ara
- Departamento
de Física Aplicada and Instituto Universitario de Materiales
de Alicante (IUMA), Universidad de Alicante, Campus de San Vicente del Raspeig, Alicante E-03690, Spain
| | - L. Pastor-Amat
- Departamento
de Física Aplicada and Instituto Universitario de Materiales
de Alicante (IUMA), Universidad de Alicante, Campus de San Vicente del Raspeig, Alicante E-03690, Spain
| | - C. Untiedt
- Departamento
de Física Aplicada and Instituto Universitario de Materiales
de Alicante (IUMA), Universidad de Alicante, Campus de San Vicente del Raspeig, Alicante E-03690, Spain
| | - E. B. Lombardi
- Department
of Physics, Florida Science Campus, University
of South Africa, Florida
Park, Johannesburg 1710, South Africa
| | - W. Dednam
- Department
of Physics, Florida Science Campus, University
of South Africa, Florida
Park, Johannesburg 1710, South Africa
| | - C. Sabater
- Departamento
de Física Aplicada and Instituto Universitario de Materiales
de Alicante (IUMA), Universidad de Alicante, Campus de San Vicente del Raspeig, Alicante E-03690, Spain
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2
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García-Blázquez MA, Dednam W, Palacios JJ. Nonequilibrium Magneto-Conductance as a Manifestation of Spin Filtering in Chiral Nanojunctions. J Phys Chem Lett 2023; 14:7931-7939. [PMID: 37646507 PMCID: PMC10494227 DOI: 10.1021/acs.jpclett.3c01922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Accepted: 08/10/2023] [Indexed: 09/01/2023]
Abstract
It is generally accepted that spin-dependent electron transmission may appear in chiral systems, even without magnetic components, as long as significant spin-orbit coupling is present in some of its elements. However, how this chirality-induced spin selectivity (CISS) manifests in experiments, where the system is taken out of equilibrium, is still debated. Aided by group theoretical considerations and nonequilibrium DFT-based quantum transport calculations, here we show that when spatial symmetries that forbid a finite spin polarization in equilibrium are broken, a net spin accumulation appears at finite bias in an arbitrary two-terminal nanojunction. Furthermore, when a suitably magnetized detector is introduced into the system, the net spin accumulation, in turn, translates into a finite magneto-conductance. The symmetry prerequisites are mostly analogous to those for the spin polarization at any bias with the vectorial nature given by the direction of magnetization, hence establishing an interconnection between these quantities.
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Affiliation(s)
- M. A. García-Blázquez
- Departamento
de Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - W. Dednam
- Department
of Physics, Science Campus, University of
South Africa, Florida
Park, Johannesburg 1710, South Africa
| | - J. J. Palacios
- Departamento
de Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
- Condensed
Matter Physics Center (IFIMAC), Universidad
Autónoma de Madrid, E-28049 Madrid, Spain
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3
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Dednam W, García-Blázquez MA, Zotti LA, Lombardi EB, Sabater C, Pakdel S, Palacios JJ. A Group-Theoretic Approach to the Origin of Chirality-Induced Spin-Selectivity in Nonmagnetic Molecular Junctions. ACS Nano 2023; 17:6452-6465. [PMID: 36947721 PMCID: PMC10100547 DOI: 10.1021/acsnano.2c11410] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 03/16/2023] [Indexed: 06/18/2023]
Abstract
Spin-orbit coupling gives rise to a range of spin-charge interconversion phenomena in nonmagnetic systems where certain spatial symmetries are reduced or absent. Chirality-induced spin-selectivity (CISS), a term that generically refers to a spin-dependent electron transfer in nonmagnetic chiral systems, is one such case, appearing in a variety of seemingly unrelated situations ranging from inorganic materials to molecular devices. In particular, the origin of CISS in molecular junctions is a matter of an intense current debate. Here, we derive a set of geometrical conditions for this effect to appear, hinting at the fundamental role of symmetries beyond otherwise relevant quantitative issues. Our approach, which draws on the use of point-group symmetries within the scattering formalism for transport, shows that electrode symmetries are as important as those of the molecule when it comes to the emergence of a spin-polarization and, by extension, to the possible appearance of CISS. It turns out that standalone metallic nanocontacts can exhibit spin-polarization when relative rotations which reduce the symmetry are introduced. As a corollary, molecular junctions with achiral molecules can also exhibit spin-polarization along the direction of transport, provided that the whole junction is chiral in a specific way. This formalism also allows the prediction of qualitative changes of the spin-polarization upon substitution of a chiral molecule in the junction with its enantiomeric partner. Quantum transport calculations based on density functional theory corroborate all of our predictions and provide further quantitative insight within the single-particle framework.
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Affiliation(s)
- W. Dednam
- Department
of Physics, Florida Science Campus, University
of South Africa, 1710 Johannesburg, South Africa
| | - M. A. García-Blázquez
- Departamento
de Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - Linda A. Zotti
- Departamento
de Física Teórica de la Materia Condensada, Universidad Autonoma de Madrid, E-28049 Madrid, Spain
- Condensed
Matter Physics Center (IFIMAC), Universidad
Autónoma de Madrid, E-28049 Madrid, Spain
| | - E. B. Lombardi
- Department
of Physics, Florida Science Campus, University
of South Africa, 1710 Johannesburg, South Africa
| | - C. Sabater
- Departamento
de Física Aplicada and Unidad asociada CSIC, Universidad de Alicante, E-03690 Alicante, Spain
| | - S. Pakdel
- CAMD, Department
of Physics, Technical University of Denmark, 2800 Lyngby, Denmark
| | - J. J. Palacios
- Departamento
de Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
- Instituto
Nicolás Cabrera (INC) and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain
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4
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Ortuño A, Reine P, Alvarez de Cienfuegos L, Marquez IR, Dednam W, Lombardi EB, Palacios JJ, Leary E, Longhi G, Mujica V, Millan A, Gonzalez T, Zotti LA, Miguel D, Cuerva JM. Chiral Single‐Molecule Potentiometers Based on Stapled ortho‐ Oligo(phenylene)ethynylenes. Angew Chem Int Ed Engl 2023. [DOI: 10.1002/ange.202218640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Affiliation(s)
- Ana Ortuño
- University of Granada: Universidad de Granada Department of Organic Chemistry Faculty of Science 18071 Granada SPAIN
| | - Pablo Reine
- University of Granada: Universidad de Granada Department of Organic Chemistry 18071 SPAIN
| | | | - Irene R Marquez
- University of Granada: Universidad de Granada Department of Organic Chemistry 18071 SPAIN
| | - Wynand Dednam
- UNISA: University of South Africa Department of Physics SOUTH AFRICA
| | | | - Juan J. Palacios
- Universidad Autónoma de Madrid: Universidad Autonoma de Madrid Departamento de Fı́sica de la Materia Condensada SPAIN
| | - Edmun Leary
- IMDEA Nanociencia: Fundacion IMDEA Nanociencia Imdea SPAIN
| | - Giovanna Longhi
- University of Brescia: Universita degli Studi di Brescia Dipartimento di Medicina Molecolare e Traslazionale ITALY
| | - Vladimiro Mujica
- Arizona State University Department of Physics Department of Physics UNITED STATES
| | - Alba Millan
- University of Granada: Universidad de Granada Department of Organic Chemistry 18071 SPAIN
| | | | - Linda A. Zotti
- Universidad Autonoma de Madrid - Campus de Cantoblanco: Universidad Autonoma de Madrid Departamento de Fı́sica Teórica de la Materia Condensada SPAIN
| | - Delia Miguel
- University of Granada: Universidad de Granada Departamento de Fisicoquímica SPAIN
| | - Juan M. Cuerva
- Facultad de Ciencias. Universidad de Granada Organic Chemistry Campus Fuentenueva 18071 Granada SPAIN
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5
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Ortuño AM, Reiné P, Álvarez de Cienfuegos L, Márquez IR, Dednam W, Lombardi EB, Palacios JJ, Leary E, Longhi G, Mujica V, Millán A, González MT, Zotti LA, Miguel D, Cuerva JM. Chiral Single-Molecule Potentiometers Based on Stapled ortho- Oligo(phenylene)ethynylenes. Angew Chem Int Ed Engl 2023; 62:e202218640. [PMID: 36806838 DOI: 10.1002/anie.202218640] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [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: 12/16/2022] [Revised: 02/17/2023] [Accepted: 02/20/2023] [Indexed: 02/22/2023]
Abstract
We report on the chemical design of chiral molecular junctions with stress-dependent conductance, whose helicity is maintained during the stretching of a single molecule junction due to the stapling of both ends of the inner helix. In the reported compounds, different conductive pathways are observed, with clearly different conductance values and plateau-length distributions, attributed to different conformations of the helical structures. The large chiro-optical responses and the potential use of these molecules as unimolecular spin filters have been theoretically proved using state-of-the-art Density Functional Theory (DFT) calculations, including a fully ab-initio estimation of the CISS-originating spin polarization which is done, for the first time, for a realistic molecular system.
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Affiliation(s)
- Ana M Ortuño
- Departamento de Química Orgánica, Universidad de Granada (UGR), Unidad de Excelencia de Química Aplicada a la Biomedicina y Medioambiente (UEQ), Facultad de Ciencias, C. U. Fuentenueva, Spain
| | - Pablo Reiné
- Departamento de Química Orgánica, Universidad de Granada (UGR), Unidad de Excelencia de Química Aplicada a la Biomedicina y Medioambiente (UEQ), Facultad de Ciencias, C. U. Fuentenueva, Spain
| | - Luis Álvarez de Cienfuegos
- Departamento de Química Orgánica, Universidad de Granada (UGR), Unidad de Excelencia de Química Aplicada a la Biomedicina y Medioambiente (UEQ), Facultad de Ciencias, C. U. Fuentenueva, Spain
| | - Irene R Márquez
- Departamento de Química Orgánica, Universidad de Granada (UGR), Unidad de Excelencia de Química Aplicada a la Biomedicina y Medioambiente (UEQ), Facultad de Ciencias, C. U. Fuentenueva, Spain
| | - Wynand Dednam
- Department of Physics, University of South Africa, Science Campus, Private Bag X6, Florida Park, 1710, South Africa
| | - Enrico B Lombardi
- Department of Physics, University of South Africa, Science Campus, Private Bag X6, Florida Park, 1710, South Africa
| | - Juan J Palacios
- Departamento de Física de la Materia Condensada, Instituto Nicolás Cabrera (INC) and IFIMAC, Universidad Autónoma de Madrid, Cantoblanco, 28049, Madrid, Spain
| | - Edmund Leary
- Fundación IMDEA Nanociencia, 28049, Madrid, Spain
| | - Giovanna Longhi
- Dipartimento di Medicina Molecolare e Traslazionale, Universitá di Brescia, Viale Europa 11, 25121, Brescia, Italy
| | - Vladimiro Mujica
- School of Molecular Sciences, Arizona State University, Tempe, AZ 85287, USA.,Kimika Fakultatea, Euskal Herriko Unibertsitatea (UPV/EHU), P.K. 1072, 20018, Donostia, Euskadi, Spain.,Departamento de Fisicoquímica, Universidad de Granada (UGR), (UEQ), Facultad de Ciencias, C. U. Fuentenueva, Spain
| | - Alba Millán
- Departamento de Química Orgánica, Universidad de Granada (UGR), Unidad de Excelencia de Química Aplicada a la Biomedicina y Medioambiente (UEQ), Facultad de Ciencias, C. U. Fuentenueva, Spain
| | | | - Linda A Zotti
- Departamento de Física Teórica de la Materia Condensada and IFIMAC, Universidad Autónoma de Madrid, Cantoblanco, 28049, Madrid, Spain
| | - Delia Miguel
- Departamento de Fisicoquímica, Universidad de Granada (UGR), (UEQ), Facultad de Ciencias, C. U. Fuentenueva, Spain
| | - Juan M Cuerva
- Departamento de Química Orgánica, Universidad de Granada (UGR), Unidad de Excelencia de Química Aplicada a la Biomedicina y Medioambiente (UEQ), Facultad de Ciencias, C. U. Fuentenueva, Spain
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6
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Zotti LA, Dednam W, Lombardi EB, Palacios JJ. Constrained DFT for Molecular Junctions. Nanomaterials (Basel) 2022; 12:nano12071234. [PMID: 35407352 PMCID: PMC9002544 DOI: 10.3390/nano12071234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 03/31/2022] [Accepted: 04/04/2022] [Indexed: 02/01/2023]
Abstract
We have explored the use of constrained density functional theory (cDFT) for molecular junctions based on benzenediamine. By elongating the junction, we observe that the energy gap between the ionization potential and the electronic affinity increases with the stretching distance. This is consistent with the trend expected from the electrostatic screening. A more detailed analysis shows how this influences the charge distribution of both the individual metal layers and the molecular atoms. Overall, our work shows that constrained DFT is a powerful tool for studying screening effects in molecular junctions.
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Affiliation(s)
- Linda Angela Zotti
- Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
- Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain;
- Correspondence:
| | - Wynand Dednam
- Department of Physics, Science Campus, University of South Africa, Private Bag X6, Florida Park 1710, South Africa; (W.D.); (E.B.L.)
| | - Enrico B. Lombardi
- Department of Physics, Science Campus, University of South Africa, Private Bag X6, Florida Park 1710, South Africa; (W.D.); (E.B.L.)
| | - Juan Jose Palacios
- Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain;
- Departamento de Física de la Materia Condensada and Instituto Nicolás Cabrera (INC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain
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7
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Dednam W, Caturla MJ, Botha AE, SanFabián E, Miralles JA, Louis E. Probability distribution for heat exchange in plastic deformation. Phys Rev E 2021; 104:034101. [PMID: 34654188 DOI: 10.1103/physreve.104.034101] [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: 05/06/2021] [Accepted: 08/20/2021] [Indexed: 11/07/2022]
Abstract
Fluctuation theorems allow one to obtain equilibrium information from nonequilibrium experiments. The probability distribution function of the relevant magnitude measured along the irreversible nonequilibrium trajectories is an essential ingredient of fluctuation theorems. In small systems, where fluctuations can be larger than average values, probability distribution functions often deviate from being Gaussian, showing long tails, mostly exponential, and usually strongly asymmetric. Recently, the probability distribution function of the van Hove correlation function of the relevant magnitude was calculated, instead of that of the magnitude itself. The resulting probability distribution function is highly symmetric, obscuring the application of fluctuation theorems. Here, the discussion is illustrated with the help of results for the heat exchanged during plastic deformation of aluminum nanowires, obtained from molecular dynamics calculations. We find that the probability distribution function for the heat exchanged is centrally Gaussian, with asymmetric exponential tails further out. By calculating the symmetry function we show that this distribution is consistent with fluctuation theorems relating the differences between two equilibrium states to an infinite number of nonequilibrium paths connecting those two states.
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Affiliation(s)
- W Dednam
- Department of Physics, Science Campus, University of South Africa, Florida Park, Johannesburg 1710, South Africa.,Instituto Universitario de Materiales de Alicante (IUMA), Universidad de Alicante, San Vicente del Raspeig, E-03690 Alicante, Spain.,Departamento de Física Aplicada, Universidad de Alicante, San Vicente del Raspeig, E-03690 Alicante, Spain
| | - M J Caturla
- Instituto Universitario de Materiales de Alicante (IUMA), Universidad de Alicante, San Vicente del Raspeig, E-03690 Alicante, Spain.,Departamento de Física Aplicada, Universidad de Alicante, San Vicente del Raspeig, E-03690 Alicante, Spain
| | - A E Botha
- Department of Physics, Science Campus, University of South Africa, Florida Park, Johannesburg 1710, South Africa
| | - E SanFabián
- Instituto Universitario de Materiales de Alicante (IUMA), Universidad de Alicante, San Vicente del Raspeig, E-03690 Alicante, Spain.,Unidad Asociada of the "Consejo Superior de Investigaciones Científicas," Universidad de Alicante, San Vicente del Raspeig, E-03690 Alicante, Spain.,Departamento de Química Física, Universidad de Alicante, San Vicente del Raspeig, E-03690 Alicante, Spain
| | - J A Miralles
- Instituto Universitario de Materiales de Alicante (IUMA), Universidad de Alicante, San Vicente del Raspeig, E-03690 Alicante, Spain.,Departamento de Física Aplicada, Universidad de Alicante, San Vicente del Raspeig, E-03690 Alicante, Spain
| | - E Louis
- Instituto Universitario de Materiales de Alicante (IUMA), Universidad de Alicante, San Vicente del Raspeig, E-03690 Alicante, Spain.,Departamento de Física Aplicada, Universidad de Alicante, San Vicente del Raspeig, E-03690 Alicante, Spain.,Unidad Asociada of the "Consejo Superior de Investigaciones Científicas," Universidad de Alicante, San Vicente del Raspeig, E-03690 Alicante, Spain
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