Optimized Single-Configuration Wavefunction for the Ground State of Lithium Fluoride

Abstract

A single‐configuration self‐consistent‐field molecular orbital wavefunction for the ¹Σ ground state of lithium fluoride from which a total molecular energy of —106.9885 a.u. at an internuclear separation of 2.8877 a.u. can be calculated is reported. It is shown on the basis of correlation energy arguments that this energy is within 0.007 a.u. of the Hartree—Fock energy for the ground state of this molecule. Results computed with wavefunctions of slightly lower accuracy (—106.9769 a.u. at the minimum in the computed potential energy curve) are reported over a range of internuclear separations from 1.6 to 4.85 a.u. The systematic approach used in obtaining the best wavefunction is described, since it appears to be a reasonable approach from the point of view of minimizing the amount of calculation involved, and for molecular wavefunctions this is a crucial consideration. A comprehensive table of expectation values including the dipole moment, kinetic energy T, potential energy V, $${\displaystyle \sum _i}{r}_{\mathrm{Li}\mathrm{,i}}^2\mathrm{,\hspace{0.17em}\hspace{0.17em}}{\displaystyle \sum _i}{\text{1/r}}_{\mathrm{Li}\mathrm{,i}}\mathrm{,\hspace{0.17em}\hspace{0.17em}}{\displaystyle \sum _i}{\text{1/r}}_{\mathrm{F}\mathrm{,i}}\mathrm{,\hspace{0.17em}\hspace{0.17em}}{\displaystyle \sum _{\text{1<j}}}{\text{1/r}}_{\mathrm{ij}},$$ and ${\displaystyle \sum _i}{\text{(3z}}_{\mathrm{Li}\mathrm{,i}}^2{\mathrm{-r}}_{\mathrm{Li}\mathrm{,i}}^2)$ computed with wavefunctions of varying degrees of approximation is given.