As a first step in the modelling of a family of organic crystals, I
consider using the simple Buckingham potential of Gavezzotti and Filippini
(in: Computational Approaches in Supramolecular Chemistry, G. Wipff,
ed. Kluwer, pp. 51-62 (1994)).
However, the A,B,C parameters in the _expression_ E=Aexp(-BR)-C/R^6 do
not obey the usual combinations rules.
On the other hand, it seems that the Tinker program I use does expect
such rules.
Is it nonetheless possible to specify independent A,B,C parameters
for each atom pair to the program, or is it necessary to modify the programs
in order to introduce the extra degree of freedom required ?
Sincerely yours.
-- Didier MATHIEU CEA - Le Ripault, BP 16 37260 Monts (France) Tel. 33(0)2.47.34.41.85