The ICA (Intermolecular Contacts Analysis) computer program was developed for statistical analysis of intermolecular atom-atom contacts in organic crystals. At present, the program allows one to examine homomolecular crystals belonging to monosystem structural classes. The analysis involves the following steps: selection of supporting contacts (i.e., contacts sufficient for the formation of a three-dimensional framework of intermolecular "touches"), construction of their distributions over atom-atom distances, approximation of the distribution curves by Gaussians, and calculations of the average (most probable) length of the contacts of a particular type and the variance of the distribution. The van der Waals radii of the most important organogenic elements were refined on the basis of the data on approximately 7800 crystal structures retrieved from the Cambridge Structural Database. (c) 2005 Pleiades Publishing, Inc.
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