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>From lou_at_degas.scripps.edu Tue Jun 20 13:03 PDT 2000
Date: Tue, 20 Jun 2000 13:03:22 -0700 (PDT)
From: Lou Noodleman <lou_at_scripps.edu>
To: duke_at_citrin.chemie.uni-dortmund.de
Subject: Re: ADF-LIST: Protonation energies
Cc: lou_at_scripps.edu

Dear Frank Glahe,
Your problem is almost certainly the reference state in ADF, which is
the sum of the spin restricted atoms. Thus, protonated adenine has an
additional spin restricted H-atom in the reference state.
 The ionization potential of the "restricted"
H atom is 12.633eV=291.3 Kcal/mol., calculated for a VBP potential-for example,
see C.L. Fisher et al., J.Phys.Chem. 100,13498, 1996.
 You must correct for this process:
H(res)-> H+ +1e-(at infinity). (Note that the corresponding spin-polarized
H-atom has an IP=13.58eV, close to exp. 13.6058eV). You can calculate these
IP's yourself, using the ADF programs. It may be helpful to have a small
fraction of 1e-, say one-millionth, in your calculation of the "bare proton"
(H+) state, since the program is expecting a non-zero electron density.
All of this is well known to those doing protonation (or deprotonation)
calculations with ADF.
Lou Noodleman
Molecular Biology
The Scripps Research Institute
La Jolla, CA
.

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Received on 2000-06-21 19:55:16