A THEORETICAL-STUDY OF THE (H-2)2 DIMER .3. THE ISOTROPIC POTENTIAL

An extended geminal model has been applied to calculate the isotropic potential of the (H-2)2 dimer within the rigid rotor approximation. By adopting a [6s,4p,3d,2f] contracted Gaussian type basis set and the numerical model EXRHF3, 16 different distances from 3 to 12 au are considered. The isotropic potential is calculated directly by approximating it by the value of the potential for one particular orientation of the molecule. It is demonstrated that this last approximation induces an error of less than 1%. The calculated isotropic potential presents a minimum of 108.9 muhartree at a distance of 6.58 au, in close agreement with experimentally based results.