Showing papers by "K. T. Tang published in 1997"

Multipolar polarizabilities and two- and three-body dispersion coefficients for alkali isoelectronic sequences

Abstract: Using simple wave functions based on the asymptotic behavior and on the binding energies of the valence electron, we have evaluated multipolar matrix elements. They allow us to obtain polarizabilities up to α12 of Li, Na, K, Rb, Cs, Be+, Mg+, Ca+, Sr+, Ba+, and dispersion coefficients of homonuclear and heteronuclear interactions from c6 to c24. Comparisons with previously determined low order quantities show that this approach is capable of yielding quite useful values for these quantities.

Van der Waals potentials of He2, Ne2, and Ar2 with the exchange energy calculated by the surface integral method

Abstract: A simple semiempirical potential for two-body multielectron systems is developed. The repulsion is obtained from the exchange energy that is calculated with the surface integral method. The main component of the attraction comes from the second-order polarization energy given by the damped dispersion series. The small contributions of the first-order polarization energy and the overlap integrals to the van der Waals potential are examined. Without any adjustable parameters, this theory is shown to give accurate potential curves for the He2, Ne2, and Ar2 systems. By absorbing the first-order polarization energy into the exchange energy expression and neglecting the small contribution of the overlap integrals, this theory reduces to the successful Tang–Toennies potential model.

Exchange energy of H2 calculated by the surface integral method with the Coulson–Fischer wave function

Abstract: The exchange energy of the H2 molecule in the chemical bond region is calculated by the surface integral method with the well known Coulson–Fischer wave function. Compared with the triplet–singlet energy difference from separate electronic structure calculations, the surface integral method is shown to be simple and accurate.