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Title: Second derivatives for approximate spin projection methods

The use of broken-symmetry electronic structure methods is required in order to obtain correct behavior of electronically strained open-shell systems, such as transition states, biradicals, and transition metals. This approach often has issues with spin contamination, which can lead to significant errors in predicted energies, geometries, and properties. Approximate projection schemes are able to correct for spin contamination and can often yield improved results. To fully make use of these methods and to carry out exploration of the potential energy surface, it is desirable to develop an efficient second energy derivative theory. In this paper, we formulate the analytical second derivatives for the Yamaguchi approximate projection scheme, building on recent work that has yielded an efficient implementation of the analytical first derivatives.
Authors:
;  [1]
  1. Chemistry and Chemical Biology, University of California, Merced, California 95343 (United States)
Publication Date:
OSTI Identifier:
22416066
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 5; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; APPROXIMATIONS; ELECTRONIC STRUCTURE; ERRORS; IMPLEMENTATION; POTENTIAL ENERGY; RADICALS; SPIN; STRAINS; SURFACES; SYMMETRY BREAKING; TRANSITION ELEMENTS