ORTHOGONALLY SPIN-ADAPTED SINGLE-REFERENCE COUPLED-CLUSTER FORMALISM - LINEAR-RESPONSE CALCULATION OF HIGHER-ORDER STATIC PROPERTIES

An algorithm for the calculation of nth-order static properties of clo sed-shell systems is formulated and implemented, up to and including f ourth order, using an orthogonally spin-adapted coupled-cluster (CC) l inear response (LR) method. Cluster operators are truncated at the sin gle and double excitation level (CCSD-LR approach) and previously publ ished [A. E. Kondo et al., J. Chem. Phys. 102, 6511 (1995)] first-orde r CCSD-LR equations, in terms of molecular integrals and zeroth- and f irst-order cluster amplitudes, are generalized to an arbitrary order. Static properties, including electrostatic dipole and quadrupole momen ts, polarizabilities and hyperpolarizabilities, are calculated for the lowest singlet state of CH2 and for the ground state of HF at both eq uilibrium and displaced geometries. The advantages of the LR formalism vs the finite field approach, particularly when evaluating higher-ord er properties for highly stretched geometries, are pointed out. (C) 19 96 American Institute of Physics.