Hapka M, Przybytek M, Pernal K. Symmetry-Adapted Perturbation Theory Based on Multiconfigurational Wave Function Description of Monomers.
J Chem Theory Comput 2021;
17:5538-5555. [PMID:
34517707 PMCID:
PMC8444344 DOI:
10.1021/acs.jctc.1c00344]
[Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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We present a formulation
of the multiconfigurational (MC) wave
function symmetry-adapted perturbation theory (SAPT). The method is
applicable to noncovalent interactions between monomers which require
a multiconfigurational description, in particular when the interacting
system is strongly correlated or in an electronically excited state.
SAPT(MC) is based on one- and two-particle reduced density matrices
of the monomers and assumes the single-exchange approximation for
the exchange energy contributions. Second-order terms are expressed
through response properties from extended random phase approximation
(ERPA). The dispersion components of SAPT(MC) have been introduced
in our previous works [HapkaM.2019, 15, 1016−102730525591; HapkaM.2019, 15, 6712–672331670950]. SAPT(MC) is applied either with generalized valence
bond perfect pairing (GVB) or with complete active space self-consistent
field (CASSCF) treatment of the monomers. We discuss two model multireference
systems: the H2 ··· H2 dimer
in out-of-equilibrium geometries and interaction between the argon
atom and excited state of ethylene. Using the C2H4* ··· Ar complex as an example, we examine second-order
terms arising from negative transitions in the linear response function
of an excited monomer. We demonstrate that the negative-transition
terms must be accounted for to ensure qualitative prediction of induction
and dispersion energies and develop a procedure allowing for their
computation. Factors limiting the accuracy of SAPT(MC) are discussed
in comparison with other second-order SAPT schemes on a data set of
small single-reference dimers.
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