From owner-chemistry@ccl.net Tue Jun 9 20:40:01 2015 From: "Gustavo L.C. Moura gustavo.moura|a|ufpe.br" To: CCL Subject: CCL: Proper way of doing a Boltzmann average Message-Id: <-51436-150609203805-12713-syM2I3ZlDGcdGmdqzELiPQ]![server.ccl.net> X-Original-From: "Gustavo L.C. Moura" Date: Tue, 9 Jun 2015 20:37:58 -0400 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