Tests of approximate methods for the calculation of the static potential for electron scattering by CO

Abstract

The interaction potential between an electron and an unperturbed CO molecule is calculated as a function of the electron's position r (measured with the origin at the center of mass of CO) by the INDO (intermediate-neglect-of-differential-overlap) molecular orbital theory and by an approximate application (following Itikawa and Takayanagi) of Massey's method. The results are compared quantitatively to the ab initio extended-basis-set molecular orbital calculation of Gianturco and Tait. The potential is expanded as V(r) = ΣLVL(r)PL(r̂·R̂), where R̂ is a unit vector along the internuclear axis. The INDO VL(r) is fairly accurate for L = 0, 2, and 4 but not for L = 1. The approximate Massey's method calculation is fairly accurate only for r < 2.3 bohr for L = 0, 2, and 4.