Contributions to interatomic and intermolecular forces

Abstract

Contributions to the interatomic forces between two H atoms in the ³Σ _u ⁺ state are examined using the VB approach. In particular, it is found that the charge transfer contribution, which is relatively small at the van der Waals minimum, grows to be larger than the dispersion contribution at R = 4·0 Bohr. The problems associated with the entanglement of the charge transfer contribution and the basis set enhancement error are discussed, and it is shown that the error is essentially missing in these calculations. Thus, a reliable estimate of charge transfer is arrived at.