CCL: Proper way of doing a Boltzmann average

 Sent to CCL by: "Gustavo L.C. Moura" [gustavo.moura%x%ufpe.br]
 Dear CCL community,
 I am seeking advice about the proper way of calculating a Boltzmann average.
 For the sake of argument, let us say that I have a molecule that may assume only
 two distinct conformations A and B. I have no problems calculating the Boltzmann
 averaged property in this case.
 However, I have strong theoretical and experimental evidences that my molecule
 forms a hydrogen bonded dimer. The dimerization process does not affect the
 flexibility of each monomer and they still have the same two conformations A and
 B as before. I have no problems dealing with the averaging process for the
 dimers in conformations AA and BB (they are unique). My problem is with
 conformations AB and BA. The two dimers can be superimposed (and are technically
 equal), but I still know which monomer has each conformation.
 My question is: should I include both dimers in the Boltzmann average or should
 I include only one of them in the Boltzmann average?
 Your advice is most welcome.
 Thank you very much in advance.
 Sincerely yours,
 			Gustavo L.C. Moura