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Ab initio study of bond stretching: Implications in force‐field parametrization for molecular mechanics and dynamics
Author(s) -
Orozco Modesto,
Luque F.J.
Publication year - 1993
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.540140802
Subject(s) - force field (fiction) , potential energy , parametrization (atmospheric modeling) , chemistry , computational chemistry , computation , bond length , quadratic equation , formalism (music) , anharmonicity , ab initio , classical mechanics , quantum mechanics , molecule , physics , mathematics , geometry , algorithm , art , musical , organic chemistry , visual arts , radiative transfer
We report a theoretical study of the stretching of chemical bonds and its implications on the force‐field parametrization. Computations were performed at the SCF and MCSCF levels by using minimal, split‐valence, and large extended and polarized basis sets. The stretching energy profiles were determined considering up to 25 perturbed geometries of 11 different bonds (6 singles, 2 doubles, and 3 triples). The energy profiles and stretching parameters are compared with the experimental data compiled in the most popular force fields. MCSCF stretching energy profiles are mainly anharmonic and can be only roughly reproduced by quadratic equations. The use of Allinger's MM2 quasiharmonic expression appears as the best choice because it fits with reasonable accuracy a large percentage of the stretching profile without increasing the complexity of the formalism and of the parametrization procedure. MCSCF computations are needed to obtain reliable stretching force parameters. In this respect, MCSCF calculations considering as active space only the bonded and nonbonded orbitals of the perturbed bond seems to be the best strategy to obtain good results at a minimum computational cost, especially if small split‐valence basis sets like the 3‐21G are used. Results obtained at this level of sophistication are completely comparable to stretching parameters compiled on empirical force fields. © 1993 John Wiley & Sons, Inc.