ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
Simple formulae for the interaction energy between two molecules have been used for writing a program which evaluates the total interaction energy of the molecules in a crystal. These formulae appear as sums of atom-atom and, eventually, atom-bond and bond-bond contributions. The non-additivity of the polarization energy is taken into account, and a rough estimate of the third-order non-additive terms ('triple dipole') is introduced. A suitable modification of the formulae for short interatomic distances allows us to treat hydrogen-bond interactions as well. We present results for the crystals of CH4, CO2, C6H6, and C6H5NO2. The energies calculated for the experimental geometry are in good agreement with experiment. For CO2 and C6H5NO2 minimizations of the computed energy (with respect to unit cell parameters and orientation and position of one molecule in the cell) were performed and it was found that the experimental configuration actually was very close to a minimum. The configurations of neighbour molecules in the crystal are compared with the optimal configuration of a binary complex, and it appears that, for non-hydrogen-bonded molecules, significant differences between these configurations may occur. Finally, for nitrobenzene several local minima seem to exist on the energy hypersurface; the minimum corresponding to the known experimental geometry appears to be the lowest, but only by a small amount.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0567739475001015
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