Conditions for Describing Triplet States in Reduced Density Matrix Functional Theory

Θεοφίλου, Ίρις; Lathiotakis, N. N.; Helbig, Nicole

doi:10.1021/acs.jctc.6b00257

Cited by 10 publications

(10 citation statements)

References 49 publications

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“…Based on this expected implication of (quasi)pinning as an effect in the one-particle picture on the structure of the N-fermion quantum states, variational ansatzes for ground states have been proposed as part of an ongoing development [47][48][49][50][51]. Moreover, general investigations and deeper insights into the structure of quantum states suggest that taking the GPCs into account may help to turn RDMFT into a more competitive method [52,53] (for more specific results see [50,54,55]). In particular, it has been shown [56] for all translationally invariant one-band lattice systems (regardless of their dimensionality, size and interactions) that the gradient of the exact universal functional diverges repulsively on the polytope boundary ¶.…”

Section: Potential Physical Relevance Of the Gpcsmentioning

confidence: 99%

“…Moreover, general investigations and deeper insights into the structure of quantum states suggest that taking the GPCs into account may help to turn Reduced Density Matrix Functional Theory (RDMFT) into a more competitive method [52,53] (for more specific results see Refs. [50,54,55]). In particular, it has been shown [56] for all translationally invariant one-band lattice systems (regardless of their dimensionality, size and interactions) that the gradient of the exact universal functional diverges repulsively on the polytope boundary ∂P.…”

Section: Potential Physical Relevance Of the Generalized Pauli Constr...mentioning

confidence: 99%

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Implications of pinned occupation numbers for natural orbital expansions: I. Generalizing the concept of active spaces

et al. 2020

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The concept of active spaces simplifies the description of interacting quantum many-body systems by restricting to a neighborhood of active orbitals around the Fermi level. The respective wavefunction ansatzes which involve all possible electron configurations of active orbitals can be characterized by the saturation of a certain number of Pauli constraints   n 0 1 i , identifying the occupied core orbitals (n i =1) and the inactive virtual orbitals (n j =0). In Part I, we generalize this crucial concept of active spaces by referring to the generalized Pauli constraints. To be more specific, we explain and illustrate that the saturation of any such constraint on fermionic occupation numbers characterizes a distinctive set of active electron configurations. A converse form of this selection rule establishes the basis for corresponding multiconfigurational wavefunction ansatzes. In Part II, we provide rigorous derivations of those findings. Moroever, we extend our results to non-fermionic multipartite quantum systems, revealing that extremal single-body information has always strong implications for the multipartite quantum state. In that sense, our work also confirms that pinned quantum systems define new physical entities and the presence of pinnings reflect the existence of (possibly hidden) ground state symmetries.

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Section: Potential Physical Relevance Of the Gpcsmentioning

confidence: 99%

Section: Potential Physical Relevance Of the Generalized Pauli Constr...mentioning

confidence: 99%

Implications of pinned occupation numbers for natural orbital expansions: I. Generalizing the concept of active spaces

et al. 2020

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“…Among the methods that go beyond density functional theory, density matrix functional theory (DMFT) [15][16][17][18][19][20][21][22][23][24][25], can also tackle static correlation problems. This method will be adopted and discussed in the present work.…”

Section: Introductionmentioning

confidence: 99%

Approximate density matrix functionals applied to hetero-atomic bond dissociation

van Meer,

Chai

2020

Preprint

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“…the eigenfunctions of the 1RDM are treated to be the same in both spin channels while the occupation numbers can differ. While this treatment is correct for spin singlets and states with maximum total spin S, generally open-shell systems with a different total spin cannot be treated accurately this way [21].…”

Section: Introductionmentioning

confidence: 99%

Structure of the first order reduced density matrix in three electron systems: A generalized Pauli constraints assisted study

Θεοφίλου

Lathiotakis

Helbig

2018

The Journal of Chemical Physics

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We investigate the structure of the one-body reduced density matrix of three electron systems, i.e., doublet and quadruplet spin configurations, corresponding to the smallest interacting system with an open-shell ground state. To this end, we use configuration interaction (CI) expansions of the exact wave function in Slater determinants built from natural orbitals in a finite dimensional Hilbert space. With the exception of maximally polarized systems, the natural orbitals of spin eigenstates are generally spin dependent, i.e., the spatial parts of the up and down natural orbitals form two different sets. A measure to quantify this spin dependence is introduced and it is shown that it varies by several orders of magnitude depending on the system. We also study the ordering issue of the spin-dependent occupation numbers which has practical implications in reduced density matrix functional theory minimization schemes, when generalized Pauli constraints (GPCs) are imposed and in the form of the CI expansion in terms of the natural orbitals. Finally, we discuss the aforementioned CI expansion when there are GPCs that are almost "pinned."

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Conditions for Describing Triplet States in Reduced Density Matrix Functional Theory

Cited by 10 publications

References 49 publications

Implications of pinned occupation numbers for natural orbital expansions: I. Generalizing the concept of active spaces

Implications of pinned occupation numbers for natural orbital expansions: I. Generalizing the concept of active spaces

Approximate density matrix functionals applied to hetero-atomic bond dissociation

Structure of the first order reduced density matrix in three electron systems: A generalized Pauli constraints assisted study

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