Analysis of and remedies for unphysical ground states of the multireference averaged coupled-pair functional

David B. Krisiloff, Victor B. Oyeyemi, Florian Libisch, Emily A. Carter

Research output: Contribution to journalArticle

7 Scopus citations

Abstract

A Multireference Configuration Interaction (MRCI) wavefunction includes both static and dynamic electron correlation. MRCIs well-known flaw, a lack of size extensivity, can be ameliorated with the Multireference Averaged Coupled-Pair Functional (MRACPF). However, the original MRACPF is frequently unstable, sometimes producing unphysical results. The more Multireference Averaged Quadratic Coupled-Cluster and MRACPF2 functionals also occasionally exhibit unphysical behavior. We find that these instabilities are avoided crossings with unphysical solutions to the MRACPF equations. We present two approaches to avoid the undesirable unphysical solutions.

Original languageEnglish (US)
Article number024102
JournalJournal of Chemical Physics
Volume140
Issue number2
DOIs
StatePublished - Jan 14 2014

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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