Ab. Kumar et al., AN EXTENDED COUPLED-CLUSTER FUNCTIONAL FOR MOLECULAR-PROPERTIES - STUDY OF AN ANALYTICAL AND NUMERICAL APPROACH, Chemical physics letters, 295(3), 1998, pp. 189-194
A stationary coupled-cluster method using an extended coupled-cluster
functional for molecular properties is tested. A recently developed an
alytical derivative code using non-relaxed orbitals in an approximate
singles and doubles scheme is compared with the numerical finite-field
results incorporating the relaxation of the orbitals. For this study,
the dipole moment and polarizability values of HF at different intern
uclear distances and CH+ are compared in the two schemes. A critical d
iscussion of the relaxation effects incorporated in the numerical meth
od and the approximations in the functional is presented. (C) 1998 Els
evier Science B.V. All rights reserved.