Can a single-reference approach provide a balanced description of ground and excited states? A comparison of the completely renormalized equation-of-motion coupled-cluster method with multireference quasidegenerate perturbation theory near a conical intersection and along a photodissociation coordinate in ammonia

Shikha Nangia, Donald G. Truhlar, Michael J. McGuire, Piotr Piecuch

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

We calculated the two lowest electronically adiabatic potential energy surfaces of ammonia in the region of the conical intersection and at a sequence of geometries along which one of the N-H bonds is broken. We employed both a multireference (MR) method and a single-reference (SR) method. The MR calculations are based on multiconfiguration quasidegenerate perturbation theory (MC-QDPT) with a 6-311+G(3df,3pd) basis set. The SR calculations, carried out with the same basis, employ the completely renormalized equation-of-motion coupled-cluster method with singles and doubles, and a noniterative treatment of triples, denoted CR-EOMCCSD(T). At 91 geometries used for comparison, including geometries near a conical intersection, the surfaces agree to 7% on average.

Original languageEnglish (US)
Pages (from-to)11643-11646
Number of pages4
JournalJournal of Physical Chemistry A
Volume109
Issue number51
DOIs
StatePublished - Dec 29 2005
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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