<i>Ab initio</i>theory of spin entanglement in atoms and molecules

Pittalis, Stefano; Troiani, Filippo; Rozzi, Carlo Andrea; Vignale, Giovanni

doi:10.1103/physrevb.91.075109

Cited by 9 publications

(5 citation statements)

References 33 publications

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“…They are in fact extremely relevant for all those studies and applications where a semilocal model of the KED is important. Here we suggest, for example, the evaluation of local indicators such as the electron localization function (ELF) [89,90] or the entanglement length [91]. These are density indicators but they are actually obtained as orbital-dependent expressions due to the presence of τ KS .…”

Section: Discussionmentioning

confidence: 99%

Laplacian-dependent models of the kinetic energy density: Applications in subsystem density functional theory with meta-generalized gradient approximation functionals

Śmiga,

Fabiano,

Constantin

et al. 2017

Preprint

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The development of semilocal models for the kinetic energy density (KED) is an important topic in density functional theory (DFT). This is especially true for subsystem DFT, where these models are necessary to construct the required non-additive embedding contributions. In particular, these models can also be efficiently employed to replace the exact KED in meta-Generalized Gradient Approximation (meta-GGA) exchange-correlation functionals allowing to extend the subsystem DFT applicability to the meta-GGA level of theory.Here, we present a two-dimensional scan of semilocal KED models as linear functionals of the reduced gradient and of the reduced Laplacian, for atoms and weakly-bound molecular systems. We find that several models can perform well but in any case the Laplacian contribution is extremely important to model the local features of the KED. Indeed a simple model constructed as the sum of Thomas-Fermi KED and 1/6 of the Laplacian of the density yields the best accuracy for atoms and weakly-bound molecular systems. These KED models are tested within subsystem DFT with various meta-GGA exchange-correlation functionals for non-bonded systems, showing a good accuracy of the method.

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Section: Discussionmentioning

confidence: 99%

Laplacian-dependent models of the kinetic energy density: Applications in subsystem density functional theory with meta-generalized gradient approximation functionals

Śmiga,

Fabiano,

Constantin

et al. 2017

Preprint

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“…Function t GBP ðrÞ is found to be related to the first spectral moment of the optical conductivity tensor, therefore t GBP ðrÞ reflects some electron localization properties. That explains why the electronic kinetic energy density is a part of several localization and metallicity descriptors (as ELF, LOL, and some others [117][118][119] ). Also, it is shown that the previously introduced PS-FID, describing local information about electron momentum in the position space, is somewhat similar with PVD function.…”

Section: Su M M a R Ymentioning

confidence: 99%

Spatially resolved characterization of electron localization and delocalization in molecules: Extending the Kohn‐Resta approach

Astakhov

Tsirelson

2018

Int J of Quantum Chemistry

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In this work, the electron organization of many‐electron systems is considered in a context of the linear response theory extending the Kohn‐Resta view on electron localization phenomenon. The variances of the local electronic position and momentum operators are linked via the fluctuation‐dissipation theorem to the optical conductivity tensor, that is, to observable spectroscopic properties. It is demonstrated that the electron position variance density quantifies a degree of electron delocalization in each point of position space and distinguishes between metallic and insulating character of electronic states. The momentum variance density estimates a degree of electron localization and is immediately related to electronic kinetic energy density in the Ghosh‐Berkowitz‐Parr form giving a physical interpretation to the later. We show that electron localization and delocalization phenomena in atoms and molecules can be probed by external electric field. This approach provides new electronic descriptors distinguishing and quantifying chemical bonds of different types.

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“…Analyses of electron localization are also important because they offer insights for improving density functional constructions 10 . The ELF has been connected to the ability of density functional approximations to access local information on the spin-entanglement 11 , to properties of the electronic stress tensor 12 , and to timedependent density functionals 13 . The interpretation of the ELF, however, is not free from difficulties 14,15 .…”

Section: Introductionmentioning

confidence: 99%

Bonds, lone pairs, and shells probed by means of on-top dynamical correlations

et al. 2018

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The Electron Localization Function (ELF) by Becke and Edgecombe [J. Chem. Phys. 92, 5397 (1990)] is routinely adopted as a descriptor of atomic shells and covalent bonds. Since the ELF and its related quantities find useful exploitation also in the construction of modern density functionals, the interest in complementing the ELF is linked to both the quests of improving electronic structure descriptors and density functional approximations. The ELF uses information which is available by considering parallel-spin electron pairs in single-reference many-body states. In this work, we complement this construction with information obtained by considering antiparallel-spin pairs whose short-range correlations are modeled by a density functional approximation. As a result, the approach requires only a contained computational effort. Applications to a variety of systems show that, in this way, we gain a spatial description of the bond in H2 (which is not available with the ELF) together with some trends not optimally captured by the ELF in other prototypical situations.

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Ab initiotheory of spin entanglement in atoms and molecules

Cited by 9 publications

References 33 publications

Laplacian-dependent models of the kinetic energy density: Applications in subsystem density functional theory with meta-generalized gradient approximation functionals

Laplacian-dependent models of the kinetic energy density: Applications in subsystem density functional theory with meta-generalized gradient approximation functionals

Spatially resolved characterization of electron localization and delocalization in molecules: Extending the Kohn‐Resta approach

Bonds, lone pairs, and shells probed by means of on-top dynamical correlations

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