Consistent calculation of diabatic energies and diabatic coupling terms in the van der Waals region: Application to the system

In this work we carry out calculations of the long-range interactions between a ground state O atom and a hydrogen molecule at Cs geometries in order to describe the diabatic and adiabatic surfaces that connect the 3Π and 3Σ states at collinear geometries with the 3B1, 3B2 and 3A2 states at C2v configurations. We show that the usual procedure to correct the basis set superposition error gives inconsistent results for the diabatic potentials and their coupling terms. Consistent results can only be obtained using high quality basis sets for which this error can be negligible.