Gaussian expansions for polyatomic molecules

A method for obtaining finite series expansions of Slater-type atomic orbitals in terms of an arbitrary number of Gaussian-type functions is described. The method is based on numerical quadrature procedures applied to the Laplace transform of the exponential radial dependence of the Slater orbital. Accuracy of the expansions is evaluated by examining various overlap and one-electron energy integrals. A further application is made to the evaluation of two-centre Coulomb electron repulsion integrals and it is seen that six-place accuracy is obtainable using sixteen term expansions.