Projected seniority-two orbital optimization of the antisymmetric product of one-reference orbital geminal

Katharina Boguslawski; Paweł Tecmer; Peter A Limacher; Paul A Johnson; Paul W Ayers; Patrick Bultinck; Stijn De Baerdemacker; Dimitri Van Neck

doi:10.1063/1.4880820

Projected seniority-two orbital optimization of the antisymmetric product of one-reference orbital geminal

J Chem Phys. 2014 Jun 7;140(21):214114. doi: 10.1063/1.4880820.

Authors

Katharina Boguslawski¹, Paweł Tecmer¹, Peter A Limacher¹, Paul A Johnson¹, Paul W Ayers¹, Patrick Bultinck², Stijn De Baerdemacker³, Dimitri Van Neck³

Affiliations

¹ Department of Chemistry and Chemical Biology, McMaster University, Hamilton, 1280 Main Street West, Ontario L8S 4M1, Canada.
² Department of Inorganic and Physical Chemistry, Ghent University, Krijgslaan 281 (S3), 9000 Gent, Belgium.
³ Center for Molecular Modelling, Ghent University, Technologiepark 903, 9052 Gent, Belgium.

PMID: 24907997
DOI: 10.1063/1.4880820

Abstract

We present a new, non-variational orbital-optimization scheme for the antisymmetric product of one-reference orbital geminal wave function. Our approach is motivated by the observation that an orbital-optimized seniority-zero configuration interaction (CI) expansion yields similar results to an orbital-optimized seniority-zero-plus-two CI expansion [L. Bytautas, T. M. Henderson, C. A. Jimenez-Hoyos, J. K. Ellis, and G. E. Scuseria, J. Chem. Phys. 135, 044119 (2011)]. A numerical analysis is performed for the C2 and LiF molecules, for the CH2 singlet diradical as well as for the symmetric stretching of hypothetical (linear) hydrogen chains. For these test cases, the proposed orbital-optimization protocol yields similar results to its variational orbital optimization counterpart, but prevents symmetry-breaking of molecular orbitals in most cases.