Anharmonic force fields from analytic CCSD(T) second derivatives: HOF and F_2O

摘要

The recent implementation of analytic second derivatives for CCSD(T) (coupled cluster theory with single and double excitations augmented by a perturbational treatment of connected triple excitations) has been combined with a numerical finite difference procedure to calculate cubic and semidiagonal quartic force fields. Computational details of this approach are outlined. Applications are reported for HOF and F_2O. The CCSD(T) results are in excellent agreement with experiment and represent a substantial improvement over the results obtained from MP2 (Moller-Plesset second-order perturbation theory).