Multiconfigurational Effects on the Density Coherence

Dayou Zhang, Donald G. Truhlar

Research output: Contribution to journalArticlepeer-review

Abstract

This paper is a study of density coherences in multiconfiguration self-consistent field theory and Kohn-Sham (KS) density functional theory. We visualize and compare the nondiagonal elements of the first-order reduced density matrix in the electronic coordinate representation. This is the electronic density coherence, and it also appears in Hartree-Fock (HF) theory in the integrand of the exchange integral. The density coherence is calculated as a function of the internuclear distance for three diatomic molecules (H2, F2, and HF) using both restricted and unrestricted KS and HF theory, as well as the complete active space self-consistent field method. We identify a group of closely associated peaks corresponding to the coherence of electrons on opposite sides of the center of the molecule, and we call this the exchange massif. We find that Slater-determinant methods with a higher percentage of HF exchange tend to underestimate the density coherence at the exchange massif. We explain the trends in terms of a multireference diagnostic and the number of unpaired electrons.

Original languageEnglish (US)
Pages (from-to)6915-6925
Number of pages11
JournalJournal of Chemical Theory and Computation
Volume16
Issue number11
DOIs
StatePublished - Nov 10 2020

Bibliographical note

Funding Information:
We thank Chen Zhou and Ben Janesko for helpful discussions. This research was supported in part by the Air Force Office of Scientific Research by grant FA9550-16-1-0134.

PubMed: MeSH publication types

  • Journal Article

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