Difference of potential surface of HF and B3LYP - A Case of H2, H2+ and H2- -

Abstract

Potential energy surfaces of H2, H2+ and H2- molecules calculated by B3LYP with 6-311G** basis set are compared with those by Hartree-Fock (HF). H2+ has no exchange correlation and electron correlation. H2 has exchange correlation and electron correlation. H2- has larger exchange correlation and electron correlation than H2. In the case of H2, potential surfaces of HF and B3LYP are almost the same not only in equilibrium region but also in long inter-atomic distance region. However, potential surfaces of H2+ and H2- generated by B3LYP are different from those of HFs, especially in long inter-atomic distance region. The potential surfaces have maximum at about 3Å and are qualitatively wrong at long distance.