Subject: intermolecular interactions

From: [email-masked] (mforster)
Date: Fri, 13 Mar 1998 11:48:42 GMT

Dear Net Chemists

Could some Quantum chemistry experts please offer some advice or
comments on the computation of intermolecular interactions by
quantum methods. 

I noticed a recent paper in which the the difference in the (SCF) 
energy of an ion pair at some separation (r) relative to the the sum
of the energies of the individual ions was used to estimate the stabilisation
of the ion pair. Does this approach neglect basis set superposition effects 
where the 'effective' basis set size grows as the two separate molecules
are brought together. In addition how would such calculations be affected 
by numerical basis sets (eg as used by DMOL).    

  Dr Mark J Forster Ph.D.
  Principal Scientist
  Informatics Laboratory
  National Institute for Biological Standards and Control
  Blanche Lane, South Mimms, 
  Hertfordshire EN6 3QG, United Kingdom.

  Tel 	01707 654753
  FAX 	01707 646730
  E-mail 	[email-masked]