Projected quasiparticle theory for molecular electronic structure

Gustavo E. Scuseria, Carlos A. Jiménez-Hoyos, Thomas M. Henderson, Kousik Samanta, Jason K. Ellis
2011 Journal of Chemical Physics  
We derive and implement symmetry-projected Hartree-Fock-Bogoliubov (HFB) equations and apply them to the molecular electronic structure problem. All symmetries (particle number, spin, spatial, and complex conjugation) are deliberately broken and restored in a self-consistent variation-after-projection approach. We show that the resulting method yields a comprehensive black-box treatment of strong correlations with effective one-electron (mean-field) computational cost. The ensuing wave function
more » ... is of multireference character and permeates the entire Hilbert space of the problem. The energy expression is different from regular HFB theory but remains a functional of an independent quasiparticle density matrix. All reduced density matrices are expressible as an integration of transition density matrices over a gauge grid. We present several proof-of-principle examples demonstrating the compelling power of projected quasiparticle theory for electronic structure theory.
doi:10.1063/1.3643338 pmid:21974513 fatcat:yzhbzvjcwrfhjac3ybailvu5te