Molecular Orbital Study of Be4

Abstract

An LCAO MO SCF study was made of the square, planar Be4 complex. A complete SCF calculation was performed at four different internuclear distances. In this series of calculations all one- and two-center integrals were evaluated exactly and the value of each three- and four-center integral was estimated by a method considered most suitable for it. The results showed the complex unstable. The energy values when extrapolated to infinite internuclear distance were in good agreement with experiment. A second series of calculations was made to determine the effect of three- and four-center integral approximations on the energies. Here all the multicenter integrals were evaluated by one type of approximation. This introduced a relatively small change in the integral values, but large changes in the energies. The study emphasizes the need for exact values of three- and four-center integrals before exact calculations can be undertaken.