A corrected valence electron approximation

A valence electron approximation is examined in which valence shell orbitals are orthogonalized to neglected core orbitals. It is possible to determine approximate upper and lower bounds to that binding energy which would be predicted by an analogous calculation with the same basis orbitals but with all electrons included. This should be useful in estimating molecular binding energies. The example of lithium hydride is discussed in detail. This technique is particularly appropriate for investigation of the stability of hitherto unknown rare gas compounds.