A SIMPLE-MODEL FOR PREDICTING STRUCTURES OF GAS-PHASE VANDERWAALS DIMERS CONTAINING A RARE-GAS ATOM

A computationally simple model for predicting the preferred structures of gas-phase dimers containing a rare-gas atom is developed and tested. The structures are determined by minimizing the multicenter interaction energy arising from dispersive attraction counterbalanced by hard-sphere repulsion. In the absence of readily available good quality intramolecular atomic polarizability data, it is shown that the geometrical anisotropy of the dispersive interaction can be satisfactorily modeled by replacing atomic polarizabilities with cubes of covalent radii of the bound atoms. The model is found to accurately reproduce the structures of most known dimers containing a rare-gas atom and leads to a number of useful insights into the results for several dimers. The only significant failure of the model is for linear dimers and this is clearly ascribed to the deficiency in modeling the repulsive van der Waals shell and the necessity for including the inductive term. The ease of applicability makes the model an attractive add-on term for calculations on systems where anisotropy of the dispersive interaction may be important, in particular for other types of weakly bound complexes.