Improving half-projected spin-contaminated wave functions by multi-configuration perturbation theory

Zsuzsanna É Mihálka; Ágnes Szabados; Péter R Surján

doi:10.1063/5.0053727

Improving half-projected spin-contaminated wave functions by multi-configuration perturbation theory

J Chem Phys. 2021 Jun 21;154(23):234110. doi: 10.1063/5.0053727.

Authors

Zsuzsanna É Mihálka¹, Ágnes Szabados², Péter R Surján²

Affiliations

¹ Laboratory of Theoretical Chemistry, Institute of Chemistry, Faculty of Science, and George Hevesy Doctoral School of Chemistry, ELTE Eötvös Loránd University, H-1518 Budapest 112, P.O. Box 32, Budapest, Hungary.
² Laboratory of Theoretical Chemistry, Institute of Chemistry, Faculty of Science, ELTE Eötvös Loránd University, H-1518 Budapest 112, P.O. Box 32, Budapest, Hungary.

PMID: 34241248
DOI: 10.1063/5.0053727

Abstract

Allowing triplet components of individual geminals, spin-contaminated strongly orthogonal geminal wave functions may emerge, which can be ameliorated by spin-projection techniques. Of the latter, half-projection was previously shown to be useful, offering a compromise between the amount of remaining spin-contamination and the violation of size consistency generated by projection. This paper investigates how a half-projected spin-contaminated geminal wave function can be improved by multi-configuration perturbation theory to incorporate dynamical correlation effects.