Small Gaussian Expansions of Atomic Orbitals

Expansions of Clementi STO SCF AO's for some first-row atoms with GTO's have been obtained by the method of least squares. Expansion lengths vary from two to five Gaussians for each AO. In addition, Gaussian sets with constraints that the exponential parameters be shared for 1s and 2s and 2s and 2p orbital expansions are reported. For all cases a full matrix least-squares procedure was employed whereby the expansion coefficients and exponential parameters were simultaneously varied. All orbital expansions were constrained to a normalization condition. These expansions are useful for computing x-ray scattering factors and can be used in quantum-chemical studies.