The crystal-held exerted on a single molecule is approximated by a cluster
of molecules placed at their crystallographic positions around the probe mo
lecule. The vibrational dynamics of the probe molecule are calculated using
semi-emprical methods. Observed INS spectra are compared with those calcul
ated from the cluster model and an isolated molecule. (C) 2000 Elsevier Sci
ence B.V. All rights reserved.