Semiempirical calculation of van der Waals coefficients for alkali-metal and alkaline-earth-metal atoms

The van der Waals coefficients, C-6, C-8, and C-10 for the alkali-metal (Li, Na, K, and Rb) and alkaline-earth-metal (Be, Mg, Ca, and Sr) atoms are estimated by a combination of ab initio and semiempirical methods. Polarizabilities and atom-wall coefficients are given as a diagnostic check, and the lowest order nonadiabatic dispersion coefficient, D-8 and the three-body coefficient, C-9 are also presented. The dispersion coefficients are in agreement with the available relativistic many-body perturbation theory calculations. The contribution from the core was included by using constrained sum rules involving the core polarizability and Hartree-Fock expectation values to estimate the f-value distribution

Interaction Potentials for He-F- and Ne-F-

[[abstract]]Ab initio potential energy curves for the interaction of a fluoride anion with a He atom and a Ne atom are obtained by supermolecular CCSD(T) calculations, that is, coupled cluster calculations in the space of single and double substitutions corrected noniteratively for triple substitutions. The computations include full counterpoise corrections and employ large basis sets with bond functions. The CCSD(T) potential energy curves have significantly deeper wells than their many-body perturbation theory counterparts. Fits to functional forms that reproduce the CCSD(T) points with an average absolute error less than 0.3% are reported. � 1998 American Institute of Physics