Asymptotics of the exchange-splitting energy for a diatomic molecular ion from a volume-integral formula of symmetry-adapted perturbation theory

Piotr Gniewek and Bogumił Jeziorski
Phys. Rev. A 90, 022506 – Published 12 August 2014

Abstract

The exchange-splitting energy J of the lowest gerade and ungerade states of the H2+ molecular ion was calculated using a volume integral expression of symmetry-adapted perturbation theory and standard basis set techniques of quantum chemistry. The performance of the proposed expression was compared to the well-known surface-integral formula. Both formulas involve the primitive function, which we calculated employing either the Hirschfelder-Silbey perturbation theory or the conventional Rayleigh-Schrödinger perturbation theory (the polarization expansion). Our calculations show that very accurate values of J can be obtained using the proposed volume-integral formula. When the Hirschfelder-Silbey primitive function is used in both formulas the volume formula gives much more accurate results than the surface-integral expression. We also show that using the volume-integral formula with the primitive function approximated by Rayleigh-Schrödinger perturbation theory, one correctly obtains only the first four terms in the asymptotic expansion of the exchange-splitting energy.

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  • Received 10 May 2014

DOI:https://doi.org/10.1103/PhysRevA.90.022506

©2014 American Physical Society

Authors & Affiliations

Piotr Gniewek* and Bogumił Jeziorski

  • Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland

  • *pgniewek@tiger.chem.uw.edu.pl
  • jeziorsk@chem.uw.edu.pl

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Vol. 90, Iss. 2 — August 2014

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