Am Die, 20 Jun 2000 schrieben Sie:
> It just occured to me: could it be that you take the energy of the proton as
> zero? Note that if you compute the energy of AdH(+) in ADF, you get the
> energy difference between AdH(+) and its fragments (at least in my version
> of ADF). The proper fragment for H is the hydrogen atom, NOT the proton, so
> you need to account for the difference in energy between proton and H
That's the point. I am not able to get the energetical difference between
proton and hydrogen by means of "bonding enegy", as there is no bond. Your
suggestion with h2O and H3O+ is a good one, I had tried it already, I got
better results, but obviously this is only a proton migration. I have also
tried to calc an Ade+ (without H) and the attach to this fragment a H , I got
better results also, but again, not in the region of the exp. and Gaussian
results. I have thought about instead of trying this addition with Water,
realizing this with H2 and H3+, as the H+ in this molecule is not really bound.
But again it would be not the best way... I have tought about this for almost 5
weeks and I am not able to overcome this problem, so when ypu have any further
suggestions, I am pleased to hear about them
> > -----Original Message-----
> > From: Louwen, J. (Jaap)
> > Sent: Tuesday, June 20, 2000 1:00 PM
> > To: 'duke_at_citrin.chemie.uni-Dortmund.de'
> > Subject: RE: ADF-LIST: Protonation energies
> > With energies differences of that kind something is obviously wrong.
> > Without knowing further details, it is hard tell what went wrong, but on a
> > general note I would stick to the principle: rely as much on compensation
> > of error as possible.
> > That is: do not try to compute the energy of the reaction Ad + H(+) ->
> > AdH(+) but refer to a reaction like:
> > Ad + H3O(+) -> AdH(+) + H2O
> > This has the definite advantage that the number of bonds doesn't change
> > (and the character doesn't change much), so there will substantial
> > cancellation of model errors. From the energy of the reaction last given
> > and an experimental value for the protonation of H2O, you should be able
> > to derive proper values.
> > Incidentally, one of the soures of errors might be the basis set
> > superposition error (BSSE) - only if you don't use ghost atoms, of course.
> > However, those errors tend to be less significant in DFT than in
> > Hartree-Fock.
> > Regards
> > Jaap N. Louwen
> > Akzo Nobel Catalysts BV site Amsterdam-N
> > Research Center Catalysts - dept. SMA
> > PO box 37650
> > 1030 BE Amsterdam
> > The Netherlands
> > Phone: +31 20 634 7486
> > fax: +31 20 634 7653
> > email: jaap.louwen_at_akzonobel.com,
> > private email address: louwen.spiekerman_at_hetnet.nl
> > -----Original Message-----
> > From: Frank Glahe AC-III C2-05-329 Tel.3747
> > [SMTP:duke_at_data.Chemie.Uni-Dortmund.DE]
> > Sent: Monday, June 19, 2000 9:33 AM
> > To: adflist
> > Subject: ADF-LIST: Protonation energies
> > Dear all,
> > We have tried to investigate the protonation energies of Adenine
> > with ADF and
> > encountered a small, but yet annoying problem. We have obtained
> > values, that
> > are about 280 kcal/mole higher than results in G98 and gas phase
> > measurements. These two are in line.
> > My question is, how do I calculate the protonation energy properly?
> > F.Glahe
-- **** WWW http://www.chemie.uni-dortmund.de/groups/lippert/ MAIL uch480_at_pop.uni-dortmund.de TEL +49 231 755 3747 FAX +49 231 755 3797 ****Received on 2000-06-20 13:46:43
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