Calculation of exchange forces between molecules by application of the Hellmann-Feynman theorem

Abstract

The computation of exchange forces between molecules can be performed about 20 times faster by using the Hellmann-Feynman theorem than by the usual energy methods. The accuracy of the results for He₂, He-H₂, (H₂O)₂ and (C₂H₄)₂ is disappointing, however, particularly in the region of the Van der Waals minimum.