Fundamental Role of Fock Exchange in Relativistic Density Functional Theory

Desmarais, Jacques K.; Flament, Jean‐Pierre; Erba, Alessandro

doi:10.1021/acs.jpclett.9b01401

Cited by 21 publications

(28 citation statements)

References 54 publications

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“…We then look into the dependence of spin polarization in CISS on modeling decisions, as in particular the admixture of exact exchange in the approximate exchange–correlation functional. This is important since the imaginary part of the effective single-particle Hamiltonian matrix (in a framework including SOC) depends on it , (for recent work on the importance of exact exchange for SOC, also see refs and ). Finally, we do a representative check of how our findings for an artificial system transfer to realistic systems, by varying the exact exchange admixture for the spin polarization in a helicene derivative.…”

Section: Introductionmentioning

confidence: 99%

Influence of Electronic Structure Modeling and Junction Structure on First-Principles Chiral Induced Spin Selectivity

Zöllner

Saghatchi

Mújica

et al. 2020

J. Chem. Theory Comput.

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We have carried out a comprehensive study of the influence of electronic structure modeling and junction structure description on the first-principles calculation of the spin polarization in molecular junctions caused by the chiral induced spin selectivity (CISS) effect. We explore the limits and the sensitivity to modeling decisions of a Landauer/Green's function/two-component density functional theory approach to CISS. We find that although the CISS effect is entirely attributed in the literature to molecular spin filtering, spin−orbit coupling being partially inherited from the metal electrodes plays an important role in our calculations on ideal carbon helices, even though this effect cannot explain the experimental conductance results. Its magnitude depends considerably on the shape, size, and material of the metal clusters modeling the electrodes. Also, a pronounced dependence on the specific description of exchange interaction and spin−orbit coupling is manifest in our approach. This is important because the interplay between exchange effects and spin−orbit coupling may play an important role in the description of the junction magnetic response. Our calculations are relevant for the whole field of spinpolarized electron transport and electron transfer, because there is still an open discussion in the literature about the detailed underlying mechanism and the magnitude of physical parameters that need to be included to achieve a consistent description of the CISS effect: seemingly good quantitative agreement between simulation and the experiment can be caused by error compensation, because spin polarization as contained in a Landauer/Green's function/two-component density functional theory approach depends strongly on computational and structural parameters.

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Section: Introductionmentioning

confidence: 99%

Influence of Electronic Structure Modeling and Junction Structure on First-Principles Chiral Induced Spin Selectivity

Zöllner

Saghatchi

Mújica

et al. 2020

J. Chem. Theory Comput.

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“…In our methodology, both molecular and crystalline orbitals are expressed as linear combinations of atomic orbitals (LCAO), which is a suitable representation when chemical features of bonding are to be analyzed. Quantum-mechanical calculations are performed with a developmental version of the Crystal program, , where the LCAO approach has recently been extended to g -type basis functions. , Scalar relativistic effects must be accounted for − , and here are described by use of small-core effective pseudopotentials (with 60 electrons in the core for U). , While the program has recently been extended to the treatment of spin–orbit coupling, − this relativistic effect is disregarded here. This is because, while making the calculations significantly more demanding, it has been previously shown to induce very minor changes to chemical bonding .…”

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confidence: 99%

Charge Density Analysis of Actinide Compounds from the Quantum Theory of Atoms in Molecules and Crystals

Cossard

Desmarais

Casassa

et al. 2021

J. Phys. Chem. Lett.

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The nature of chemical bonding in actinide compounds (molecular complexes and materials) remains elusive in many respects. A thorough analysis of their electron charge distribution can prove decisive in elucidating bonding trends and oxidation states along the series. However, the accurate determination and robust analysis of the charge density of actinide compounds pose several challenges from both experimental and theoretical perspectives. Significant advances have recently been made on the experimental reconstruction and topological analysis of the charge density of actinide materials [ IUCrJ et al 2019 6 895 ]. Here, we discuss complementary advances on the theoretical side, which allow for the accurate determination of the charge density of actinide materials from quantum-mechanical simulations in the bulk. In particular, the extension of the Topond software implementing Bader’s quantum theory of atoms in molecules and crystals (QTAIMAC) to f - and g -type basis functions is introduced, which allows for an effective study of lanthanides and actinides in the bulk and in vacuo , on the same grounds. Chemical bonding of the tetraphenyl phosphate uranium hexafluoride cocrystal [PPh 4 + ][UF 6 – ] is investigated, whose experimental charge density is available for comparison. Crystal packing effects on the charge density and chemical bonding are quantified and discussed. The methodology presented here allows reproducing all subtle features of the topology of the Laplacian of the experimental charge density. Such a remarkable qualitative and quantitative agreement represents a strong mutual validation of both approaches—experimental and computational—for charge density analysis of actinide compounds.

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“…Further additions to the series will consider multireference generalizations of the theory, based on QDPT, as well as the treatment of periodic systems. This series complements work by some of the present authors to provide a program for two-component spin–current DFT calculations on periodic systems within the Crystal code. − …”

Section: Introductionmentioning

confidence: 60%

“…A comparison of the perturbation theory approach with an SV calculation, performed with our 2c-SCF implementation, also in the Crystal code, ,,− is given in Table for the members F 2 , Cl 2 , Br 2 , and I 2 of the halogen diatomic molecule series. This set of molecules was chosen because of the availability of many sets of RECPs and the large contribution of SOC to their energy.…”

Section: Computational Results For the Halogen Series Diatomic Moleculesmentioning

confidence: 99%

Perturbation Theory Treatment of Spin–Orbit Coupling, Part I: Double Perturbation Theory Based on a Single-Reference Initial Approximation

Desmarais

Erba

Flament

2021

J. Chem. Theory Comput.

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We develop a perturbation theory for solving the many-body Dirac equation within a given relativistic effective-core potential approximation. Starting from a scalar-relativistic unrestricted Hartree−Fock (SR UHF) solution, we carry out a double perturbation expansion in terms of spin−orbit coupling (SOC) and the electron fluctuation potential. Computationally convenient energy expressions are derived through fourth order in SOC, second order in the electron fluctuation potential, and a total of third order in the coupling between the two. Illustrative calculations on the halogen series of neutral and singly positive diatomic molecules show that the perturbation expansion is well-converged by taking into account only the leading (nonvanishing) term at each order of the electron fluctuation potential. Our perturbation theory approach provides a computationally attractive alternative to a two-component self-consistent field treatment of SOC. In addition, it includes coupling with the fluctuation potential through third order and can be extended (in principle) to multireference calculations, when necessary for both closed-and open-shell cases, using quasi-degenerate perturbation theory.

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Fundamental Role of Fock Exchange in Relativistic Density Functional Theory

Cited by 21 publications

References 54 publications

Influence of Electronic Structure Modeling and Junction Structure on First-Principles Chiral Induced Spin Selectivity

Influence of Electronic Structure Modeling and Junction Structure on First-Principles Chiral Induced Spin Selectivity

Charge Density Analysis of Actinide Compounds from the Quantum Theory of Atoms in Molecules and Crystals

Perturbation Theory Treatment of Spin–Orbit Coupling, Part I: Double Perturbation Theory Based on a Single-Reference Initial Approximation

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