We develop a consistent procedure for introducing an external single-particle potential into the cluster expansion of the energy expectation value with respect to a correlated wave function. It is shown that the usual Brueckner reaction-matrix approximation may be extracted from the correlated-basis-functions theory by a special treatment of the external potential and an associated special choice of two-body correlation factor.

• Received 18 January 1972

DOI:https://doi.org/10.1103/PhysRevC.5.1233