Gaussian-Type Functions for Polyatomic Systems. I

In view of rapid progress of computer capability, it is very desirable to have a reliable assessment of the usefulness of Gaussian-type orbitals as basis functions for large-scale molecular calculations. In the present paper several attempts are made to answer this question mainly at the level of atomic Hartree—Fock calculations. The necessary number of terms of Gaussian-type basis functions in the analytical Hartree—Fock expansion calculation is apparently more than twice as much as the number of terms needed in the expansion with Slater-type basis functions. However, this fact does not necessarily suggest a definite choice of Slater-type orbitals. Discussions pertinent to this point are presented in the latter part of the present paper.