Premium
SCF, MP2, and CEPA‐1 calculations on the OH ‥ O hydrogen bonded complexes (H 2 O) 2 and (H 2 O‐H 2 CO)
Author(s) -
Vos R. J.,
Hendriks R.,
Van Duijneveldt F. B.
Publication year - 1990
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.540110102
Subject(s) - counterpoise , chemistry , ab initio , intermolecular force , ab initio quantum chemistry methods , binding energy , computational chemistry , bent molecular geometry , interaction energy , hydrogen bond , dispersion (optics) , crystallography , atomic physics , molecule , basis set , physics , density functional theory , organic chemistry , quantum mechanics
Counterpoise corrected ab initio calculations are reported for (H 2 O) 2 and H 2 O‐H 2 CO. Geometry searches were done in the moment‐optimized basis DZP' at the SCF, MP2, and CEPA‐1 levels of theory, followed by more accurate single‐point calculations in basis ESPB, which includes bondfunctions to saturate the dispersion energy. The final equilibrium binding energies obtained are −4.7 ±0.3 kcal/mol for a near‐linear (H 2 O) 2 structure and −4.6 ±0.3 kcal/mol for a strongly bent HOH ‥ OCH 2 structure. The energy difference between these systems is much smaller than in all previous ab initio work. Cyclic ( C 2 h ) and bifurcated ( C 2 v ) transition structures for (H 2 O) 2 are located at 1.0 ±0.1 kcal/mol and 1.9 ±0.3 kcal/mol above the global minimum, respectively. A new partitioning scheme is presented that rigorously partitions the MP2 correlation interaction energy in intra and intermolecular (dispersion) contributions. These terms are large (up to 2 kcal/mol) but of opposite sign for most geometries studied and hence their overall effect upon the final structures is relatively small. The relative merits of the MP2 and CEPA‐1 approaches are discussed are discussed and it is concluded that for economical reasons MP2 is to be preferred, especially for larger systems.