Molecular properties from coupled-cluster Brueckner orbitals

We investigate to which extent a single determinant made up from orbitals obtained by a Brueckner coupled-cluster doubles calculation is able to reproduce correlated one-electron properties. It is shown that dipole and quadrupole moments and radial expectation values compare quite well with BCCD finite-freld results for a test selection of nine molecules enclosing HF, H2O, NH3, CO, N-2, NO+, HCN, CuH and CH3OH and three rare-gas atoms He, Ne and Ar. Furthermore, we find that even second-order properties such as dipole and quadrupole polarizabilities are reproduced fairly well when determined as first derivatives of the corresponding Brueckner orbital expectation values. (C) 1999 Elsevier Science B.V. All rights reserved.