ACCURACY OF COUNTERPOISE CORRECTIONS IN 2ND-ORDER INTERMOLECULAR POTENTIAL CALCULATIONS .2. VARIOUS MOLECULAR DIMERS

Using the method of localized second-order pair correlations for weak interactions as developed previously, we have evaluated the overcorrection of the counterpoise method for various molecular dimers. In all cases, for large basis sets the overcorrection is small, even though the counterpoise correction itself can be very large. In some cases if the basis set is poor, there remain serious overcorrections, but in general it is much better to use the counterpoise correction than to ignore it. Specifically we consider molecules such as hydrogen, water, hydrogen fluoride, and ammonia as well as cases involving ionic interactions.