Ab-initio valence bond calculations on the He-He potential curve using small bases

In studying methods for the ab-initio calculation of Van der Waals interactions which can be extended to larger molecules, we have tested the Valence Bond scheme on the He2 system. This method looks promising, as it appears to yield in one consistent formalism both the attractive dipole—dipole terms and the repulsive exchange terms with reasonable accuracy, using only a simple orbital basis and a very small number of VB structures.