From:	states %-% at %-% ibc.wustl.edu (David J. States)
Date:	Tue, 24 Jan 1995 20:24:52 -0600
Subject:	Re: CCL:van der Waals parameters from ab initio calc?

|> Thomas Huber wrote:
|> Could you please tell me how to derive van der Waals parameters from
|> ab initio calculations!
|> Any suggestions are wellcome (references, principles,...).

For condensed matter, there is a fundamental problem with the
derivation of non-bonded interactions from ab initio calculations on
isolated molecules.  High quality ab initio calculations include
wavefunctions with quite large spatial extents, much larger than
existence in a condensed matter environment would allow.  So, if you
are going to calculate non-bonded interactions, you need to start with
realistic calculations including multiple molecules.  The energy of
interaction is straightforward.  Deciding how much of it is "van der
Waals" is another issue.

David States


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