Accurate determination of the binding energy of the formic acid dimer: The importance of geometry relaxation

作者：Kalescky Robert^*; Kraka Elfi; Cremer Dieter

来源：Journal of Chemical Physics, 2014, 140(8): 084315.

DOI：10.1063/1.4866696

The formic acid dimer in its C-2h-symmetrical cyclic form is stabilized by two equivalent H-bonds. The currently accepted interaction energy is 18.75 kcal/mol whereas the experimental binding energy D-0 value is only 14.22 +/- 0.12 kcal/mol [F. Kollipost, R. W. Larsen, A. V. Domanskaya, M. Norenberg, and M. A. Suhm, J. Chem. Phys. 136, 151101 (2012)]. Calculation of the binding energies D-e and D-0 at the CCSD(T) (Coupled Cluster with Single and Double excitations and perturbative Triple excitations)/CBS (Complete Basis Set) level of theory, utilizing CCSD(T)/CBS geometries and the frequencies of the dimer and monomer, reveals that there is a 3.2 kcal/mol difference between interaction energy and binding energy D-e, which results from (i) not relaxing the geometry of the monomers upon dissociation of the dimer and (ii) approximating CCSD(T) correlation effects with MP2. The most accurate CCSD(T)/CBS values obtained in this work are D-e = 15.55 and D-0 = 14.32 kcal/mol where the latter binding energy differs from the experimental value by 0.1 kcal/mol. The necessity of employing augmented VQZ and VPZ calculations and relaxing monomer geometries of H-bonded complexes upon dissociation to obtain reliable binding energies is emphasized.

• 出版日期2014-2-28