Two-center nonexchange integrals over Slater orbitals

We have used computer algebra (CA) to construct general formulas for the tw o-center overlap, resonance, Coulomb and hybrid integrals over Slater orbit als (STOs). Individual formulas then were produced for the Coulomb integral s containing all combinations of K, L and M shell orbitals. The numerical e valuation of these formulas is very rapid and allows unrestricted accuracy. Tests give complete agreement with the output of numerical programs writte n by other workers. Computer algebra eliminates terms of equal magnitude an d opposite sign that can cause catastrophic loss of accuracy in a purely nu merical computation. Strong parallelization is possible in the construction and evaluation of the formulas. Their availability opens up the prospect o f carrying symbolic computation into the eigenvalue finding stage of quantu m chemistry. The present calculations also highlight several needs and oppo rtunities in the field of computer algebra. (C) 2000 American Institute of Physics. [S0021-9606(00)30445-7].