Self-consistent Field plus Dispersion Method

Self-consistent Field plus Dispersion Method 

The simplest ab initio method used to study van der Waals molecules is the Hartree-Fock method. To the Hartree-Fock interaction energy one should add the dispersion energy, which ranges from some 20% of the dissociation energy for the water dimer to twice the van der Waals well depth for He2, and is thus not negligible. The combined method may be termed SCF + Disp. 

The SCF -f- Disp method is frequently applied since it is relatively cheap and thus allows the calculation of many points on the potential energy surface. A useful potential may be obtained by empirical adjustments to the potential. For example, a damping function may be adjusted using experimental data or various components of a fitted dispersion energy may be scaled to more reasonable values . The Hartree-Fock interaction energy may also be improved, by replacing its multipole and induction components by energies derived from multipoles obtained from better calculations (e.g. Cl) or experiment cf. Refs 78 and 104-107. While these procedures may yield reasonable potentials, we feel that the predictive power of the SCF -I- Disp approach is limited. 

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A. Self-consistent Field plus Dispersion Method... 

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