Time-dependent projected Hartree-Fock

摘要: Projected Hartree-Fock (PHF) has recently emerged as an alternative approach to describing degenerate systems where static correlation is abundant, when the spin-symmetry projected. Here, we derive a set of linearized time-dependent equations for PHF in order be able access excited states. The close connection such linear-response (TDPHF) stability condition wave function discussed. Expanding this analysis also makes it possible give analytical expressions projected coupling terms Hamiltonian and overlaps between Slater determinants. TDPHF with spin-projection (TDSUHF) its Tamm-Dancoff approximation are benchmarked several electronically molecules including dissociating H2, F2 O3 at equilibrium, distorted ethylene. It shown that they consistently better descriptions states than does HF (TDHF). Furthermore, demonstrate offer not only singly but doubly states, which naturally arise upon spin-projection. We address thermodynamic limit TDSUHF, using non-interacting He gas. While tend converge those size system due lack size-extensivity PHF, remain reasonable even limit. find overall performance our method systematically regular TDHF many cases same computational scaling.