Influence of the Counterpoise Correction on the Optimized Relativi Degrees of Freedom in the H-Bonded Complex Water-Formamide

The correction of the basis set superposition error by the counterpoise method has been investigated at the SCF level for the weak H-bonded water-formamide complex and the results have been compared with the uncorrected results at the SCF, post SCF and semi-empirical AM1 and MNDO levels. Our particular concern has been the determination of the three optimized relative degrees of freedom and the relative stability of three C(s) geometrical conformations. The conclusions are that the counterpoise correction weakly conditions the variation in the degrees of freedom and the relative stabilities of the three conformers. The correction is obviously inadequate to describe intramolecular deformation.