Implementation of the incremental scheme for one-electron first-order properties in coupled-cluster theory.

A fully automated parallelized implementation of the incremental scheme for coupled-cluster singles-and-doubles (CCSD) energies has been extended to treat molecular (unrelaxed) first-order one-electron properties such as the electric dipole and quadrupole moments. The convergence and accuracy of the incremental approach for the dipole and quadrupole moments have been studied for a variety of chemically interesting systems. It is found that the electric dipole moment can be obtained to within 5% and 0.5% accuracy with respect to the exact CCSD value at the third and fourth orders of the expansion, respectively. Furthermore, we find that the incremental expansion of the quadrupole moment converges to the exact result with increasing order of the expansion: the convergence of nonaromatic compounds is fast with errors less than 16 mau and less than 1 mau at third and fourth orders, respectively (1 mau=10(-3)ea(0)(2)); the aromatic compounds converge slowly with maximum absolute deviations of 174 and 72 mau at third and fourth orders, respectively.