Knowledge Bank

An electronic wave function can be approximated near one nucleus in a molecule by expanding in terms of analytic orbitals centered on that nucleus. This expansion cannot be expected to be of practical value beyond the nearest neighbor nuclei to the center of expansion. However, it is possible to obtain reliable mean values of certain ""local"" operators which heavily weigh the electronic density in the vicinity of the center of expansion. The mean value of an operator localized at one of several inequivalent nuclei can be calculated from a one-center wave function obtained independently for that particular nucleus. Calculations on the isoelectronic systems $He2$, Lill, and Be will be described. Ground state energy curves for LiH and $He2$ have been obtained by integrating mean values of ""local"" operators, parametric derivitives of the electronic Hamiltonian, calculated by the one-center method.