On the basis set superposition error in potential surface investigations. I. Hydrogen-bonded complexes with standard basis set functions

Abstract

The basis set superposition errors on the energy of the complexes FH ⋅⋅⋅ OH2 and FH ⋅⋅⋅ NCH are investigated at the SCF level. The two-dimension energy-potential surfaces, corresponding to the slow and fast frequencies of the hydrogen bridge, are calculated without and with the counterpoise correction. The corresponding quadratic, cubic, and quartic force constants are computed. Similar calculations are reported for the electric dipole moment and its derivatives. These investigations show that the basis set superposition error: (i) does not decrease, in the vicinity of the equilibrium configuration of the complex, when standard high-quality basis sets are used; (ii) shifts the minimum of the potential surface, distorts this surface, and changes the force constants in a significant but not drastic manner.