Collect. Czech. Chem. Commun. 1998, 63, 1343-1354

Counterpoise-Corrected Potential Energy Surfaces of Simple Hydrogen-Bonded Systems

Pavel Hobzaa and Zdeněk Havlasb

a J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, 182 23 Prague 8, Czech Republic
b Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 166 10 Prague 6, Czech Republic


Geometric and energetic characteristics of various simple hydrogen-bonded complexes (water dimer, hydrogen fluoride dimer, formamide dimer, formic acid dimer, glycine dimer) have been studied by gradient optimization, which a priori eliminates the basis set superposition error (BSSE) by using the counterpoise (CP) method, as well as by the standard gradient optimization. Calculations were done at the Hartree-Fock, correlated MP2 and DFT levels with small- and medium-basis sets. The CP-corrected and standard PESs differ, depending on the theoretical level used. Larger differences were found if the correlation energy was included. Intermolecular distances from the CP-corrected PES are consistently longer, and the respective difference may be significant (≈0.1 A). The stabilization energies obtained from the CP-corrected PES are always larger than those from the standard PES. Optimization at the standard PES might result in a wrong structure. For example, the "quasi-linear" structure of the (HF)2 (global minimum) does not exist at the standard MP2/6-31G** and DFT/B3LYP/6-31G** PESs and it is found only when passing to the respective CP-corrected PESs.

Keywords: Counterpoise correction; Potential energy surfaces; Hydrogen bonds; Ab initio calculations; Quantum chemistry.