The relationship between double excitation amplitudes and Z vector components in some post-Hartree-Fock correlation methods

摘要

The relationship between Z vector components and excitation amplitudes is analyzed for severalnpost-Hartree-Fock correlation methods limited to double excitation amplitudes. An analytical for-nmula approximating the Z vector for the coupled cluster doubles method is presented and shownnto be quite accurate. This approximation is also used to determine the prefactor of the norm ofndoubly excited states in averaged coupled pair functional-type energy functionals self-consistentlynleading to better agreement with coupled cluster results. © 2011 American Institute of Physics.