Ground State Electronic Wave Function of Methane

摘要

An approximate electronic wave function for the ground state of CH4, in the equilibrium nuclear configuration, has been obtained by a variational calculation. Approximate Hartreehyphen;Fock molecular orbitals are expanded as linear combinations of a set of basis orbitals of the formf(x, y, z) exp(mdash;ar2) centered on carbon and hydrogen. Five independentsorbitals and twoporbitals on carbon are combined with one simple Gaussian orbital on each hydrogen nucleus. The parameters specifying these orbitals were obtained by preliminary variational calculations on the carbon atom. Correlation effects due to all possible Slater determinants constructed from these orbitals are calculated by a perturbation method. Parallel calculations with the same orbitals were carried out on the3Pground state of carbon. Calculated ionization potential and dissociation energy are compared with experimental values.