One-Center-Expansion—Configuration-Interaction Studies on CH4 and NH3

Abstract

One‐center‐expansion—configuration‐interaction calculations have been extended to include higher‐order spherical harmonics and extra radial factors. Calculations have also been made to study the prediction of nuclear geometry. Computations on CH₄ using as a basis set the orthonormalized Slater atomic orbitals through l=8, yielded a ground‐state energy of −39.94 a.u. Further, the inclusion of additional Schmidt orthogonalized radial factors gave much less improvement than the addition of higher spherical harmonics. The calculations with basis orbitals through l=4 on NH₃ failed to predict a nonplanar configuration of minimum energy except for the case where the basis set was truncated to include only orbitals through l=2. For the l=2 case NH₃ was predicted to have a nonplanar geometry within one degree of the experimental value.