Projected seniority-two orbital optimization of the Antisymmetric Product of one-reference orbital Geminal

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 [J. Chem. Phys., 135, 044119 (2011)]. A numerical analysis is performed for the C${}_2$, LiF and CH${}_2$ molecules 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.

7 pages, 2 figures

References in corpus (5)

• Multireference Correlation in Long Molecules with the Quadratic Scaling Density Matrix Renormalization Group
• Entanglement Measures for Single- and Multi-Reference Correlation Effects
• Quasiparticle Coupled Cluster Theory for Pairing Interactions
• Dynamical Mean-Field Theory for Quantum Chemistry
• Improving Guess Geminals for the Geminal Mean Field Configuration Interaction Method

Cited by in corpus (4)

• Downfolding of many-body Hamiltonians using active-space models: extension of the sub-system embedding sub-algebras approach to unitary coupled cluster formalisms
• Targeting excited states in all-trans polyenes with electron-pair states
• Analysis of two-orbital correlations in wavefunctions restricted to electron-pair states
• Targeting doubly-excited states with Equation of Motion Coupled Cluster theory restricted to double excitations