Abstract :
The evolution of the ground state ArClF potential energy surface including interactions of different order between the Cl and F atoms is considered by means of a simple model interpolating results of high-level ab initio calculations and directly transferable to ArnClF clusters and solids. The anisotropy of the potential is interpreted in terms of separate atom-atom contributions and exhibits a strong variation when 3-body effects are included. Effective interactions of Cl and F with Ar are obtained explicitly and found to be distorted significantly by strong intramolecular forces.