Re: CCL:Charges/bond-breaking

 The simple answer to your question is unrestricted HF theory.  The
 complicated answer is to do a lot of CI.  The problem is that as you pull
 the atoms apart you go through a singlet to triplet transition.  As the
 atoms separate further the spins on the atoms becom uncorrelated and you
 have basicly two singlets.  The correct way to handle this is with
 configuration interaction since this would allow you to mix singlet and
 triplet states.  You may well find that unrestricted HF will give you a
 reasonable approximation while always in the singlet state.
 Dr. Ross Underhill
 Royal Military College of Canada
 Kingston, Ontario
 (613) 541-6000 X6175
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    Simon Collins - Dept. Chemistry, UMIST, Manchester. M60 1QD
              Tel: 061-236-3311 x4476    Fax: 061-236-7677
                 E-mail: desmond()at()trigger.ch.umist.ac.uk
                         S.Collins()at()umist.ac.uk
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