Molecular polarizabilities and induced dipole moments in molecular mechanics

Molecular polarizabilities may be divided into either atomic contributions or bond contributions. The common way to estimate molecular polarizabilities is to assign atomic or bond parameters for each atom or bond type to fit experimental or quantum mechanical results. Ln this study we have taken a different approach. A general formula based on MM3 force constants and bond lengths was used to compute bond polarizabilities and molecular polarizabilities. New parameters for polarizabilities are not required. A fair agreement between experimental and computed molecular polarizabilities was obtained, with a RMS deviation of 0.82 Angstrom(3) (11.7%) and signed average error of 0.01 Angstrom(3) for a broad selection of 57 molecules studied. Two methods, the many-body interaction and the pair-interaction approaches, have been used to study induced dipole moments using the bond polarizabilities estimated from the new formula. The pair-interaction approximation, which involves much less computation than the many-body interaction approach, gives a satisfactory representation of induced dipole interaction. (C) 2000 John Wiley & Sons, Inc.