Are rare-gas Cl2 van der Waals molecules linear or T-shaped?

Abstract

Ab-initio potential energy surfaces have been calculated for HeCl2, NeCl2 and ArCl2 using Moller-Plesset perturbation theory to fourth order (MP4) with a large basis set that includes bond functions. Each surface has local minima for both the perpendicular and the linear configurations, and in each case the linear minimum is the deeper of the two. Low-lying bound states were calculated for each of the molecules. For HeCl2 and NeCl2 the perpendicular conformer is calculated to be more stable than the linear geometry, in agreement with experimental results. However, for ArCl2 the ground state is localized in the linear con guration in contradiction to experimental data. For this reason, the ArCl2 case was studied in considerable detail. Higher-level calculations were performed using two larger basis sets for the MP4 method and for the coupled-cluster method including single, double and perturbative triple excitations (CCSD(T) method). The higher level calculations were performed for two points, one for the ...