Comparison of a posteriori and a priori BSSE correction schemes for SCF intermolecular energies

A systematic SCF study has been undertaken to compare the conventional a posteriori Boys–Bernardi BSSE correction scheme with our recent CHA/F method in which BSSE is excluded in a priori manner. Potential curves have been obtained for nine simple hydrogen‐bonded systems by using nine different basis sets for each. It is concluded that the difference between the a posteriori BB and the a priori CHA schemes diminishes much faster when the basis set improves than BSSE disappears from the uncorrected SCF results. This fact gives an additional confidence in the CHA results, permitting one to draw the explicit conclusion that, at the SCF level of theory, the a priori CHA/F scheme can be considered the ultimate solution of the BSSE problem for weakly bonded systems.