Loewdin Alpha Function and Its Application to the Multi-Center Molecular Integral Problem Over Slater-Type Orbitals.

摘要

In this paper we trace the evolution of the Lowdin alpha-function method in its application to multi-center molecular integrals over Slater-type orbitals (STOs). As is well-known, any STO displaced from the origin can be expanded in an infinite series of spherical harmonics; the functional coefficients have been designated as Lowdin alpha functions. These alpha functions can be represented as exponentials multiplied by polynomials in the displacement distance and the radial distance. The polynomials are used to construct a C matrix with integer elements. To avoid cancellation errors in some cases, the exponentials are expanded to obtain E matrices for interior regions and F matrices for exterior regions. We believe that this careful approach to molecular integrals will succeed in producing accurate and rapid evaluation of the integrals needed in STO basis-set methods for quantum chemistry. Keywords: Molecular orbitals, Reprints. (aw)