Intermolecular forces in simple systems

Abstract A new, semi-empirical, method for the prediction of intermolecular forces introduced recently [Chem. Phys. Letters 36 (1975) 451] is assessed in the light of recently published dispersion forces coefficients and high precision SCF HF calculations of the repulsive interaction, performed by us, on closed shell spherical systems. The method is found to give very accurate predictions for systems with a small number of electrons and leads to the conclusion that those systems behave as the internal atomic correlation energy was almost independent from the interatomic distance. The extension of the method to heavier systems is discussed. Its application to the prediction of the potential in a mixture when the pure gas interactions are known is presented and the results shown to be satisfactory. The isotropic part of the interaction between two hydrogen molecules can also be described quite well using the same procedure.

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