Symmetry structured correlation in projected Hartree-Fock wavefunctions

Abstract

The projected Hartree-Fock wavefunctions are recast within the framework of the coupled cluster approach. Instead of state projection we directly symmetry adapt the broken symmetry correlation operator via the group invariant mean. The algebraic form for the cluster amplitudes is connected to the underlying symmetry group by this analytical projection, resulting in the inclusion of symmetry structured correlation effects into the wavefunction. After truncating the corresponding cluster amplitudes to a given order, equations that exploit this sparsity can be derived through the bivariational functional of the normal coupled cluster method. This prescription fills in a methodological gap in the standard couple cluster hierarchy, providing an additional means to incorporate pairing and higher order amplitude contributions. © 2009 American Institute of Physics.