Comparison between 6‐31 + bond functions and 6‐31 G* basis sets in UMP calculations of dissociation energies of the first row element compounds. I

A basis set with bond functions (6‐31G + BF) has been tested for its applicability to calculation of dissociation energies of single and multiple bonds by Moeller‐Plesset perturbation theory at the second and third orders. Results have been compared with those calculated in the 6‐31G* basis set. The 6‐31G + BF basis at the MP 2 and MP 3 levels yields better results than 6‐31G* basis and the time consumption is less as well. Consideration of the bond functions on the bonds neighboring the bond being broken has no significant influence on the dissociation energies either at the SCF or at the MP 2 levels. If both reactants and products can be characterized by two‐center bonds, the 6‐31G + BF basis and UMP2 variant of perturbation theory can be recommended for practical calculation of D e values, especially for the systems where the use of more exact bases is rather difficult.