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Title: Monte Carlo configuration interaction with perturbation corrections for dissociation energies of first row diatomic molecules: C{sub 2}, N{sub 2}, O{sub 2}, CO, and NO

Dissociation energies for the diatomic molecules C{sub 2}, N{sub 2}, O{sub 2}, CO, and NO are estimated using the Monte Carlo configuration interaction (MCCI) and augmented by a second order perturbation theory correction. The calculations are performed using the correlation consistent polarized valence “triple zeta” atomic orbital basis and resulting dissociation energies are compared to coupled cluster calculations including up to triple excitations (CCSDT) and Full Configuration Interaction Quantum Monte Carlo (FCIQMC) estimates. It is found that the MCCI method readily describes the correct behavior for dissociation for the diatomics even when capturing only a relatively small fraction (∼80%) of the correlation energy. At this level only a small number of configurations, typically O(10{sup 3}) from a FCI space of dimension O(10{sup 14}), are required to describe dissociation. Including the perturbation correction to the MCCI estimates, the difference in dissociation energies with respect to CCSDT ranges between 1.2 and 3.1 kcal/mol, and the difference when comparing to FCIQMC estimates narrows to between 0.5 and 1.9 kcal/mol. Discussions on MCCI's ability to recover static and dynamic correlations and on the form of correlations in the electronic configuration space are presented.
Authors:
;  [1] ; ;  [2]
  1. Tyndall National Institute, University College Cork, Dyke Parade, Lee Maltings, Cork (Ireland)
  2. Quantum Theory Project, 2234 New Physics Building 92, PO Box 118435, University of Florida at Gainesville, Gainesville, Florida 32611-8435 (United States)
Publication Date:
OSTI Identifier:
22255039
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 140; Journal Issue: 8; 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; DISSOCIATION; DISSOCIATION ENERGY; ELECTRON CORRELATION; ELECTRONIC STRUCTURE; EXCITATION; MONTE CARLO METHOD; NITRIC OXIDE; PERTURBATION THEORY