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

A Multireference Configuration Interaction (MRCI) wavefunction includes both static and dynamic electron correlation. MRCI's 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.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [5]
  1. Department of Chemistry, Princeton University, Princeton, New Jersey 08544-1009 (United States)
  2. Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544-5263 (United States)
  3. Institute for Theoretical Physics, Vienna University of Technology, Vienna (Austria)
  4. Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544-5263 (United States)
  5. (United States)
Publication Date:
OSTI Identifier:
22253630
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 140; Journal Issue: 2; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; CONFIGURATION INTERACTION; DEFECTS; ELECTRON CORRELATION; GROUND STATES; INSTABILITY; WAVE FUNCTIONS