On the structure of the alkaline earth dihalides dimers

A simple polarizable ion model of the Rittner type has been applied to the magnesium, calcium, strontium and barium dihalide dimers. Various energetically stable isomers were found. Structures, binding energy, vibrational frequencies and dipole moments were evaluated. At the typical temperatures of interest for these high temperature gaseous molecules the planar D2h structure has been found to be either at an absolute minimum of energy or entropy stabilized for most of the sixteen species studied. The relaxing, which could occur in inert gas matrix spectroscopy or in cluster sources, of the high temperature configurations to lower energy structures, mainly of C3v or Cs symmetry, is qualitatively discussed.