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Updated: Oct 29, 2025

Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
Published on: April 8, 2020
Improving half-projected spin-contaminated wave functions by multi-configuration perturbation theory
Zsuzsanna É Mihálka1, Ágnes Szabados2, Péter R Surján2
1Laboratory 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.
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.
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