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Shams Ghamsary M, Ghiasi M, Naghavi SS. Insight into the activation mechanism of carbonic anhydrase(II) through 2-(2-aminoethyl)-pyridine: a promising pathway for enhanced enzymatic activity. Phys Chem Chem Phys 2024; 26:10382-10391. [PMID: 38502117 DOI: 10.1039/d3cp05687b] [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] [Indexed: 03/20/2024]
Abstract
Activation of human carbonic anhydrase II (hCA II) holds great promise for treating memory loss symptoms associated with Alzheimer's disease. Despite its importance, the activation mechanism of hCA II has been largely overlooked in favor of the well-studied inhibition mechanism. To address this unexplored realm, we use first-principles calculations to tease out the activation mechanism of hCA II using 2-(2-aminoethyl)-pyridine (2-2AEPy), a promising in vitro activator. We explored both stepwise and concerted mechanisms via both available nitrogen sites of 2-2AEPy: (i) aminoethyl group (Nα) and (ii) pyridine ring (Nβ). Our results show that a concerted mechanism via Nα holds the key to hCA II activation. The activation process of the concerted mechanism exhibits the characteristics of an exergonic reaction, wherein the transition state resembles the reactant with a notably low imaginary frequency of 452.4i cm-1 and barrier height of 5.2 kcal mol-1. Such meager transition barriers propel the activation of hCA II at in vivo temperatures. These findings initiate future research into hCA II activation mechanisms and the development of efficient activators, which may lead to promising therapeutic interventions for Alzheimer's disease.
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Affiliation(s)
- Masoumeh Shams Ghamsary
- Department of Physical and Computational Chemistry, Shahid Beheshti University, Tehran 1983969411, Iran.
| | - Mina Ghiasi
- Department of Physical Chemistry and Nano chemistry, Faculty of Chemistry, Alzahra University, 1993893973, Tehran, Iran.
| | - S Shahab Naghavi
- Department of Physical and Computational Chemistry, Shahid Beheshti University, Tehran 1983969411, Iran.
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2
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Shahabfar S, Xia Y, Morshedsolouk MH, Mohammadi M, Naghavi SS. Synergistic effect of alloying on thermoelectric properties of two-dimensional PdPQ (Q = S, Se). Phys Chem Chem Phys 2023; 25:9617-9625. [PMID: 36943102 DOI: 10.1039/d2cp05979g] [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] [Indexed: 03/14/2023]
Abstract
Hosts of 2D materials exist, yet few allow compositional and structural tailoring as the MQ2 (M = Mo, W; Q = S, Se) family does, for which various structural superlattices have been synthesized. Using thorough first-principles calculations, we show how bonding hierarchy contributes to the structural resilience of 2D PdPQ and allows for full-range alloying of sulfur and selenium. Within the structural unit of Pd2P2Q2, the covalently-bonded [P2Q2]4- polyanions hold the structure together with their molecular-like P-P bonds while ionically bonded Pd-Qs allow the S/Se substitution. Here, the bonding hierarchy imparts superior electronic and structural features to the PdPQ monolayers. As such, the flat-and-dispersive valence band and the eight degenerate valleys of the conduction band benefit the p-type and n-type thermoelectricity of pristine PdPQ, which can be further enhanced by alloying. The high-entropy alloying synergistically suppresses the lattice heat transport from 75 to 30 W m-1 K-1 and increases the band degeneracy of PdPQ monolayers, resulting in an overall improvement in zT. Combining these features, in a naïve approach, results in a large zT approaching two for both p-type and n-type doping. However, accurate fully-fledged electron-phonon calculations rebut this promise, showing that at high temperatures, the increased electron scattering results in a stagnant power factor in the flat-and-dispersive valence band. Using a realistic first-principles scattering, we finally calculate the thermoelectric efficiency of PdPQ (Q = S, Se) and highlight the importance of an accurate estimation of electron relaxation time for thermoelectric predictions.
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Affiliation(s)
- S Shahabfar
- Department of Physical and Computational Chemistry, Shahid Beheshti University, Tehran 1983969411, Iran.
| | - Y Xia
- Department of Mechanical and Materials Engineering, Portland State University, Portland, Oregon, 97201, USA
| | - M H Morshedsolouk
- Department of Physical and Computational Chemistry, Shahid Beheshti University, Tehran 1983969411, Iran.
| | - M Mohammadi
- Department of Physical and Computational Chemistry, Shahid Beheshti University, Tehran 1983969411, Iran.
| | - S Shahab Naghavi
- Department of Physical and Computational Chemistry, Shahid Beheshti University, Tehran 1983969411, Iran.
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3
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Ostovan A, Papior N, Naghavi SS. Highly sensitive and low-power consumption metalloporphyrin-based junctions for CO x detection with excellent recovery. Phys Chem Chem Phys 2022; 24:14866-14876. [PMID: 35611660 DOI: 10.1039/d2cp00408a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The development of cost-effective and eco-friendly sensor materials is needed to realize the application of detectors in daily life-such as in the internet of things. In this regard, monitoring air pollutants such as carbon monoxide (CO) and carbon dioxide (CO2), mainly emitted by anthropogenic sources from daily human activities, is of great importance. In particular, developing a susceptible and portable CO2 sensor raises a dilemma because of the chemical inertness and non-polarity of CO2 molecules. We find that porphyrin-based materials, exploited by nature in biological systems, are a playground to search for such sensor materials. Using density functional non-equilibrium Green's function formalism, we fully screen all 3d metalloporphyrin (MPor) based devices to find efficient CO and CO2 gas sensors. Our detailed analysis of the adsorption energy, molecular orbitals, transmission spectra, sensitivity, and recovery time reveals that the nature of central M alters the efficiency of MPor gas detectors. We find that CO and CO2 can be monitored using, respectively, CoPor- and TiPor-based devices. The estimated sensitivity is around 100%, along with a fast recovery time at very low bias voltages (V ≥ 0.5 V), which turn metalloporphyrins into promising candidates for the widespread development of enhanced CO and CO2 sensors awaiting further experimental validations.
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Affiliation(s)
- Azar Ostovan
- Department of Physical and Computational Chemistry, Shahid Beheshti University, 1983969411 Tehran, Iran.
| | - Nick Papior
- DTU Computing Center, Department of Applied Mathematics and Computer Science, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - S Shahab Naghavi
- Department of Physical and Computational Chemistry, Shahid Beheshti University, 1983969411 Tehran, Iran.
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4
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Ostovan A, Naghavi SS. Highly Sensitive, Selective and Low-Power Consumption Metalloporphyrin−Based Junctions for Nitrogen Monoxide Detection with Excellent Recovery. Phys Chem Chem Phys 2022; 24:15579-15587. [DOI: 10.1039/d2cp01553f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Research interest in chemical gas detection has been directed towards developing highly selective bio-inspired and eco-friendly materials that allow the integration of sensors in daily human life, such as the...
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5
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Shahmohamadi H, Naghavi SS. Sulfide Perovskites for Thermoelectricity. ACS Appl Mater Interfaces 2021; 13:14189-14197. [PMID: 33734673 DOI: 10.1021/acsami.0c22842] [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] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The search for new thermoelectric materials that directly convert (waste) heat into electricity is a high-cost and time-consuming experimental effort. To facilitate this process, we perform a systematic screening for synthesizable and stable ABQ3 (A and B are metals; Q = S, Se) compounds using first-principles density functional theory calculations. A total of 40 ABQ3 compounds are predicted to be highly competent thermoelectric materials with nontoxic and earth-abundant advantages. The calculated power factors of some of them (e.g., n-type SnHfS3, p-type SbGaS3, n-type PbHfS3, and so forth) are comparable (even outperform) those of the well-known thermoelectric materials such as PbTe and Bi2Te3. The detailed analysis of electronic band structure reveals that either one or a combination of "pudding-mold" type band structure, high valley degeneracy, and high orbital degeneracy is responsible for the high PF computed in this family of materials. Taking two representative cases, we validate a low lattice thermal conductivity in ABQ3 compounds by calculating the Boltzmann transport equation using the highly accurate anharmonic lattice dynamics methods. Third-order interatomic force constants reveal that the anharmonicity and soft phonon modes, rooted in the nature of unconventional chemical bonds between the B-site metals and chalcogen atoms, lead to an ultralow lattice thermal conductivity in this family of materials. The combination of intrinsically low lattice thermal conductivity and high power factor has realized highly efficient n-type and p-type ABQ3 thermoelectric materials showing various anisotropic characteristics. Considering the thermal and moisture stability of chalcogenide perovskites, our results suggest that this unexplored family of materials is a host of highly efficient and practical thermoelectric materials awaiting further experimental validation.
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Affiliation(s)
- Hatef Shahmohamadi
- Department of Physical and Computational Chemistry, Shahid Beheshti University, Evin, 1983969411 Tehran, Iran
| | - S Shahab Naghavi
- Department of Physical and Computational Chemistry, Shahid Beheshti University, Evin, 1983969411 Tehran, Iran
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6
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Abstract
A large entropy of reduction is crucial in achieving materials capable of high-efficiency solar thermochemical hydrogen (STCH) production through two-step thermochemical water splitting cycles. We have recently demonstrated that the onsite electronic entropy of reduction attains an extreme value of 4.26 kB at 1500 K in Ce4+ → Ce3+ redox reactions, which explains the high performance and uniqueness of CeO2 as an archetypal STCH material. However, ceria requires high temperatures (T > 1500 °C) to achieve a reasonable reduction extent because of its large reduction enthalpy, which is a major obstacle in practical applications. Therefore, new materials with a large entropy of reduction and lower reduction enthalpy are required. Here, we perform a systematic screening to search for Ce4+-based oxides which possess thermodynamics superior to CeO2 for STCH production. We first search the Inorganic Crystal Structure Database (ICSD) and literature for Ce4+-based oxides and subsequently use density functional theory to compute their reduction enthalpies (i.e., oxygen vacancy formation energies). We find that CeTi2O6 with the brannerite structure is the most promising candidate for STCH because it possesses three essential characteristics of an STCH material: (i) a smaller reduction enthalpy compared to ceria yet large enough to split water, (ii) a high thermal stability, as reported experimentally, and (iii) a large entropy of reduction associated with Ce4+ → Ce3+ redox. Our proposed design strategy suggests that further exploration of Ce4+ oxides for STCH production is warranted.
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Affiliation(s)
- S Shahab Naghavi
- Department of Physical and Computational Chemistry, Shahid Beheshti University, G.C., Evin, 1983969411 Tehran, Iran
| | - Jiangang He
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - C Wolverton
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
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Balmohammadi Y, Khavasi HR, Naghavi SS. Existence of untypical halogen-involving interactions in crystal packings: a statistical and first-principles study. CrystEngComm 2020. [DOI: 10.1039/c9ce01885a] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [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
There is a common perception by the scientific community that a halogen-involving interaction forms when the distance between the donor atom and the acceptor atom is less than the sum of their van der Waals (vdW) radii.
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Affiliation(s)
- Yaser Balmohammadi
- Department of Inorganic Chemistry and Catalysis
- Shahid Beheshti University
- Tehran 1983963113
- Iran
| | - Hamid Reza Khavasi
- Department of Inorganic Chemistry and Catalysis
- Shahid Beheshti University
- Tehran 1983963113
- Iran
| | - S. Shahab Naghavi
- Department of Physical and Computational Chemistry
- Shahid Beheshti University
- 1983963113 Tehran
- Iran
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8
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Diznab MR, Maleki I, Vaez Allaei SM, Xia Y, Naghavi SS. Achieving an Ultrahigh Power Factor in Sb 2Te 2Se Monolayers via Valence Band Convergence. ACS Appl Mater Interfaces 2019; 11:46688-46695. [PMID: 31755251 DOI: 10.1021/acsami.9b14548] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
An efficient approach to improve the thermoelectric performance of materials is to converge their electronic bands, which is known as band engineering. In this regard, lots of effort has been made to further improve the thermoelectric efficiency of bulk and exfoliated monolayers of Bi2Te3 and Sb2Te3. However, ultrahigh band degeneracy and thus significant improvement of the power factor have not yet been realized in these materials. Using first-principles methods, we demonstrate that the valley degeneracy of Bi2Te3 and Sb2Te3 can be largely improved upon substitution of the middle-layer Te atoms with the more electronegative S or Se atoms. Our detailed analysis reveals that in this family of materials, two out of four possible valence band valleys merely depend on the electronegativity of the middle-layer chalcogen atoms, which makes the independent modulation of the valleys' position feasible. As such, band alignment of Bi2Te3 and Sb2Te3 largely improves upon substitution of the middle-layer Te atoms with more electronegative, yet chemically similar, S and Se ones. A superior valence band alignment is attained in Sb2Te2Se monolayers where three out of four possible valleys are well aligned, resulting in a giant band degeneracy of 18 that holds the record among all thermoelectric materials. As a result, an outstanding power factor for the hole-doped monolayers is achieved, indicating a highly efficient p-type thermoelectric material.
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Affiliation(s)
| | - Iraj Maleki
- Department of Physics , University of Tehran , Tehran 14395-547 , Iran
| | | | - Yi Xia
- Department of Materials Science and Engineering , Northwestern University , Evanston , Illinois 60208 , United States
| | - S Shahab Naghavi
- Department of Physical and Computational Chemistry , Shahid Beheshti University , G.C., Evin , Tehran 1983963113 , Iran
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Khavasi HR, Balmohammadi Y, Naghavi SS. Phenomenal Observation of Attractive Intermolecular CH⋯HC Interaction in a Mercury (II) Complex: An Experimental and First‐Principles Study. ChemistrySelect 2019. [DOI: 10.1002/slct.201901932] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Hamid Reza Khavasi
- Department of Inorganic Chemistry and CatalysisShahid Beheshti University, General Campus, Evin Tehran 1983963113 Iran
| | - Yaser Balmohammadi
- Department of Inorganic Chemistry and CatalysisShahid Beheshti University, General Campus, Evin Tehran 1983963113 Iran
| | - S. Shahab Naghavi
- Department of Physical and Computational ChemistryShahid Beheshti University, G.C., Evin 1983963113 Tehran Iran
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10
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He J, Xia Y, Naghavi SS, Ozoliņš V, Wolverton C. Designing chemical analogs to PbTe with intrinsic high band degeneracy and low lattice thermal conductivity. Nat Commun 2019; 10:719. [PMID: 30755609 PMCID: PMC6372688 DOI: 10.1038/s41467-019-08542-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [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: 05/15/2018] [Accepted: 01/03/2019] [Indexed: 11/11/2022] Open
Abstract
High-efficiency thermoelectric materials require simultaneously high power factors and low thermal conductivities. Aligning band extrema to achieve high band degeneracy, as realized in PbTe, is one of the most efficient approaches to enhance power factor. However, this approach usually relies on band structure engineering, e.g., via chemical doping or strain. By employing first-principles methods with explicit computation of phonon and carrier lifetimes, here we show two full-Heusler compounds Li2TlBi and Li2InBi have exceptionally high power factors and low lattice thermal conductivities at room temperature. The expanded rock-salt sublattice of these compounds shifts the valence band maximum to the middle of the Σ line, increasing the band degeneracy by a factor of three. Meanwhile, resonant bonding in the PbTe-like sublattice and soft Tl-Bi (In-Bi) bonding interaction is responsible for intrinsic low lattice thermal conductivities. Our results present an alternative strategy of designing high performance thermoelectric materials.
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Affiliation(s)
- Jiangang He
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - Yi Xia
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - S Shahab Naghavi
- Department of Physical and Computational Chemistry, Shahid Beheshti University, G.C., Evin, Tehran, 1983969411, Iran
| | - Vidvuds Ozoliņš
- Department of Applied Physics, Yale University, New Haven, CT, 06520, USA
- Yale Energy Sciences Institute, West Haven, CT, 06516, USA
| | - Chris Wolverton
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208, USA.
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11
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Abstract
Over the past decade, tremendous effort has been made to improve the light-harvesting ability of push-pull porphyrin dyes. Despite notable success achieved in this direction, push-pull porphyrin dyes still suffer from a poor light-harvesting efficiency owing to the lack of absorption between the Soret and Q-bands. To tackle this issue, here we design a series of push-pull porphyrin dyes with anchoring groups either at meso- or β-position using calculations based on first-principles time-dependent density functional theory. In contrast to the common perception, we find that porphyrin dyes bearing an electron-donor at the meso-position and an electron-acceptor at the β-position produce an additional extended band between the Soret and Q-bands appearing at around 500 nm due to S0 → S3 excitation, leading to a much higher light-harvesting performances compared to meso- and β-disubstituted ones. In addition, changing the π-conjugated linker at the acceptor site from ethylene linker (C═C) to acetylene linker (C≡C) further improves the light-harvesting ability of meso-β-porphyrin dyes, making them promising candidates for dye-sensitized solar cell application.
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Naghavi SS, Emery AA, Hansen HA, Zhou F, Ozolins V, Wolverton C. Giant onsite electronic entropy enhances the performance of ceria for water splitting. Nat Commun 2017; 8:285. [PMID: 28819153 PMCID: PMC5561097 DOI: 10.1038/s41467-017-00381-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [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: 02/15/2017] [Accepted: 06/20/2017] [Indexed: 11/09/2022] Open
Abstract
Previous studies have shown that a large solid-state entropy of reduction increases the thermodynamic efficiency of metal oxides, such as ceria, for two-step thermochemical water splitting cycles. In this context, the configurational entropy arising from oxygen off-stoichiometry in the oxide, has been the focus of most previous work. Here we report a different source of entropy, the onsite electronic configurational entropy, arising from coupling between orbital and spin angular momenta in lanthanide f orbitals. We find that onsite electronic configurational entropy is sizable in all lanthanides, and reaches a maximum value of ≈4.7 kB per oxygen vacancy for Ce4+/Ce3+ reduction. This unique and large positive entropy source in ceria explains its excellent performance for high-temperature catalytic redox reactions such as water splitting. Our calculations also show that terbium dioxide has a high electronic entropy and thus could also be a potential candidate for solar thermochemical reactions. Solid-state entropy of reduction increases the thermodynamic efficiency of ceria for two-step thermochemical water splitting. Here, the authors report a large and different source of entropy, the onsite electronic configurational entropy arising from coupling between orbital and spin angular momenta in f orbitals.
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Affiliation(s)
- S Shahab Naghavi
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - Antoine A Emery
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - Heine A Hansen
- Department of Energy Conversion and Storage, Technical University of Denmark, DK-2800, Kgs. Lyngby, Denmark
| | - Fei Zhou
- Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
| | - Vidvuds Ozolins
- Department of Applied Physics, Yale University, New Haven, CT, 06520, USA.,Yale Energy Sciences Institute, West Haven, CT, 06516, USA
| | - Chris Wolverton
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208, USA.
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Amsler M, Naghavi SS, Wolverton C. Prediction of superconducting iron-bismuth intermetallic compounds at high pressure. Chem Sci 2017; 8:2226-2234. [PMID: 28507678 PMCID: PMC5408563 DOI: 10.1039/c6sc04683e] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [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: 10/19/2016] [Accepted: 12/01/2016] [Indexed: 11/23/2022] Open
Abstract
We report the discovery of novel iron-bismuth compounds, FeBi2 and FeBi3, at high-pressure.
The synthesis of materials in high-pressure experiments has recently attracted increasing attention, especially since the discovery of record breaking superconducting temperatures in the sulfur–hydrogen and other hydrogen-rich systems. Commonly, the initial precursor in a high pressure experiment contains constituent elements that are known to form compounds at ambient conditions, however the discovery of high-pressure phases in systems immiscible under ambient conditions poses an additional materials design challenge. We performed an extensive multi component ab initio structural search in the immiscible Fe–Bi system at high pressure and report on the surprising discovery of two stable compounds at pressures above ≈36 GPa, FeBi2 and FeBi3. According to our predictions, FeBi2 is a metal at the border of magnetism with a conventional electron–phonon mediated superconducting transition temperature of Tc = 1.3 K at 40 GPa.
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Affiliation(s)
- Maximilian Amsler
- Department of Materials Science and Engineering , Northwestern University , Evanston , Illinois 60208 , USA . ; Tel: +1 847 467 0593
| | - S Shahab Naghavi
- Department of Materials Science and Engineering , Northwestern University , Evanston , Illinois 60208 , USA . ; Tel: +1 847 467 0593
| | - Chris Wolverton
- Department of Materials Science and Engineering , Northwestern University , Evanston , Illinois 60208 , USA . ; Tel: +1 847 467 0593
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Naghavi SS, Fabrizio M, Qin T, Tosatti E. Nanoscale orbital excitations and the infrared spectrum of a molecular Mott insulator: A15-Cs 3C 60. Nanoscale 2016; 8:17483-17488. [PMID: 27714176 DOI: 10.1039/c6nr05725j] [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] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The quantum physics of ions and electrons behind low-energy spectra of strongly correlated molecular conductors, superconductors and Mott insulators is poorly known, yet fascinating especially in orbitally degenerate cases. The fulleride insulator Cs3C60 (A15), one such system, exhibits infrared (IR) spectra with low temperature peak features and splittings suggestive of static Jahn-Teller distortions with a breakdown of orbital symmetry in the molecular site. That is puzzling, since there is no detectable static distortion, and because the features and splittings disappear upon modest heating, which they should not. Taking advantage of the Mott-induced collapse of electronic wavefunctions from lattice-extended to nanoscale localized inside a caged molecular site, we show that the unbroken spin and orbital symmetry of the ion multiplets explains the IR spectrum without adjustable parameters. This demonstrates the importance of a fully quantum treatment of nuclear positions and orbital momenta in the Mott insulator sites, dynamically but not statically distorted. The observed demise of these features with temperature is explained by the thermal population of a multiplet term whose nuclear positions are essentially undistorted, but whose energy is very low-lying. That term is in fact a scaled-down orbital excitation analogous to that of other Mott insulators, with the same spin 1/2 as the ground state, but with a larger orbital momentum of two instead of one.
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Affiliation(s)
- S S Naghavi
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
| | - M Fabrizio
- International School for Advanced Studies (SISSA), and CNR-IOM Democritos National Simulation Center, Via Bonomea 265, I-34136 Trieste, Italy.
| | - T Qin
- International School for Advanced Studies (SISSA), and CNR-IOM Democritos National Simulation Center, Via Bonomea 265, I-34136 Trieste, Italy. and Institut für Theoretische Physik, Goethe-Universität, 60438 Frankfurt am Main, Germany
| | - E Tosatti
- International School for Advanced Studies (SISSA), and CNR-IOM Democritos National Simulation Center, Via Bonomea 265, I-34136 Trieste, Italy. and International Centre for Theoretical Physics (ICTP), Strada Costiera 11, I-34151 Trieste, Italy
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15
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He J, Amsler M, Xia Y, Naghavi SS, Hegde VI, Hao S, Goedecker S, Ozoliņš V, Wolverton C. Ultralow Thermal Conductivity in Full Heusler Semiconductors. Phys Rev Lett 2016; 117:046602. [PMID: 27494488 DOI: 10.1103/physrevlett.117.046602] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Indexed: 06/06/2023]
Abstract
Semiconducting half and, to a lesser extent, full Heusler compounds are promising thermoelectric materials due to their compelling electronic properties with large power factors. However, intrinsically high thermal conductivity resulting in a limited thermoelectric efficiency has so far impeded their widespread use in practical applications. Here, we report the computational discovery of a class of hitherto unknown stable semiconducting full Heusler compounds with ten valence electrons (X_{2}YZ, X=Ca, Sr, and Ba; Y=Au and Hg; Z=Sn, Pb, As, Sb, and Bi) through high-throughput ab initio screening. These new compounds exhibit ultralow lattice thermal conductivity κ_{L} close to the theoretical minimum due to strong anharmonic rattling of the heavy noble metals, while preserving high power factors, thus resulting in excellent phonon-glass electron-crystal materials.
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Affiliation(s)
- Jiangang He
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
| | - Maximilian Amsler
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
| | - Yi Xia
- Department of Materials Science and Engineering, University of California, Los Angeles, California 90095, USA
| | - S Shahab Naghavi
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
| | - Vinay I Hegde
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
| | - Shiqiang Hao
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
| | - Stefan Goedecker
- Department of Physics, Universität Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
| | - Vidvuds Ozoliņš
- Department of Materials Science and Engineering, University of California, Los Angeles, California 90095, USA
| | - Chris Wolverton
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
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Alijani V, Winterlik J, Fecher GH, Naghavi SS, Chadov S, Gruhn T, Felser C. Quaternary Heusler compounds Co(2-x)Rh(x)MnZ (Z = Ga, Sn, Sb): crystal structure, electronic structure, and magnetic properties. J Phys Condens Matter 2012; 24:046001. [PMID: 22214567 DOI: 10.1088/0953-8984/24/4/046001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Within the huge family of Heusler compounds only a few quaternary derivatives are known that crystallize in the F43m space group. In this work, the yet unreported compounds CoRhMnZ (Z = Ga, Sn, Sb) and the alloy Co(0.5)Rh(1.5)MnSb were investigated in detail by experimental techniques and theoretical methods. The ab initio calculations predict the CoRhMnZ compounds to be half-metallic ferromagnets or to be close to the half-metallic ferromagnetic state. Calculations of the elastic constants show that the cubic structure is stable in compounds containing Mn. Both calculations and experiment reveal that Mn cannot be exchanged by Fe (CoRhFeGa). The low temperature magnetization of the compounds is in the range of 3.4-5.5 μ(B) depending on the composition. The best agreement between experiment and calculation has been achieved for CoRhMnSn (5 μ(B)). The other compounds are also cubic but tend to anti-site disorder. Compared to Co(2)MnSn it is interesting to note that the magnetic properties and half-metallicity are preserved when replacing one of the 'magnetic' Co atoms by a 'non-magnetic' Rh atom. This allows us to increase the spin-orbit interaction at one of the lattice sites while keeping the properties as a precondition for applications and physical effects relying on a large spin-orbit interaction. The Curie temperatures were determined from measurements in induction fields of up to 1 T by applying molecular field fits respecting the applied field. The highest Curie temperature was found for CoRhMnSn (620 K) that makes it, together with the other well defined properties, attractive for above room temperature spintronic applications.
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Affiliation(s)
- Vajiheh Alijani
- Institut für Anorganische und Analytische Chemie, Johannes Gutenberg-Universität, Mainz, Germany
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Abstract
This study addresses the structural and electronic properties of the NiAs- and MnP-type phases dominating in FeSe at high pressures. The analysis is performed using first-principle band structure calculations within the framework of the B3LYP hybrid exchange-correlation functional. Based on the volume-pressure relation deduced from the available experimental data, we optimize the form and internal coordinates of the unit cell, which agree reasonably well with experiment. In particular, the present calculations resolve the structural NiAs-MnP phase transition which occurs at about 10 GPa. Both structures are found to be semiconducting at low pressures and metallizing at about 80-90 GPa. Using the complementary LDA + U approach the semiconducting state can be explained as the result of the strong local correlations within the Fe d-shell.
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Affiliation(s)
- S Shahab Naghavi
- Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg Universtität, Mainz, Germany
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