For calculations of interaction potentials of weakly interacting systems, the domains of the subsystems should be determined at a very large distance and saved using the SAVE=record option on the LOCAL or MULTP cards, or the SAVE command (see section 22.4.1). If the asymptotic energy is not needed it is sufficient to do this initial calculation using option DOMONLY=1). These domains should then be reused in the subsequent calculations at all other intermolecular distances by using the START=record option or the START command (see section 22.4.2). Only in this way the basis set superposition error is minimized and normally negligible (of course, this does not affect the BSSE for the SCF, and therefore the basis set should be sufficiently large to make the SCF BSSE negligible). Usually, diffuse basis functions are important for obtaining accurate intermolecular interactions. Unfortunately, these spoil the efficiency of prescreening and therefore make direct calculations much more expensive.
For examples and discussions of these aspects see Refs. [6,7]