Re: CCL:TM force fields
Dear Dr. Bersuker
I reckon that transferability of parameters like bond distances,
(coordination-)geometries etc.
is not limited to the field of organic chemistry. Metal-ligand distances, force
constants,
torsion barriers etc. are similar in similar complexes. Hence, you can
parameterize for
inorganic
compounds in the same way as for organic compounds. As long as transferability
exists
in chemistry, force fields are possible that are not ad hoc per definition since
they
generalize
this transfereability in terms of parameters.
Yours,
Kasper
"Isaac B. Bersuker" wrote:
> Dear Dr. Norrby:
>
> Instead of getting iritated and offended, you better respond to the
specific
> criticism of the force field idea in application to TM systems. This is
SCIENCE,
> let me remind you, and the main condition of its progress is open
discussion and
> proof of statements. I proved my statements in the references I gave
earlier (that
> you deleted) and I would expect you to show that my proof is wrong. Just
stating
> that one made calculations with good results does not prove anything, with
> arbitrary parameters (changed from one compound to another) everybody can
get any a
> priori desired results.
>
> And, please, don't reffer to "authorities". I respect them all
and their point of
> view, but the scientific truth is more important.
>
> Regards
> Isaac
>
> Per-Ola Norrby wrote:
>
> > Isaac B. Bersuker wrote:
> >
> > >I repeat my firm conviction that, in general, there are
> > >no force fields for transitiom metal systems (see my latest book
...
> >
> > (The rest of the message deleted).
> >
> > I've seen this comment a couple of times now, and I'm getting
> > irritated. This is a very sweeping statement, and insulting to those
> > who have produced good work in this area. It is only true if you
> > interprete it like "it is not possible to achieve infinite
accuracy
> > for all possible TM complexes", but stated like that it would be
> > equally true of any method. For specific classes of complexes, it is
> > possible to get high accuracy with force field methods. It's just a
> > question of having a flexible enough force field and doing a careful
> > parameterization. Check out the book by Comba and Hambley,
> > "Molecular Modeling of Inorganic Compounds", a new edition
is comming
> > out soon. We also have a review in press in Coord.Chem.Rev. on how
> > to do this parameterization (don't know when it's going to appear).
> > For some classical reviews, see:
> >
> > C.R. Landis, D.M. Root, T. Cleveland, in: K.B. Lipkowitz and D.B.
> > Boyd (Eds.), Reviews in Computational Chemistry, Vol. 6, VCH
> > Publishers, Inc., New York, 1995, p. 73-148.
> >
> > M. Zimmer, Chem. Rev. 95 (1995) 2629.
> >
> > P. Comba, Comments Inorg. Chem. 16 (1994) 133.
> >
> > B.P. Hay, Coordination Chemistry Reviews 126 (1993) 177.
> >
> > (Yes, I know, I left several out, this is just a selection based on
> > personal preference).
> >
> > The general force fields are also advancing. You can still
> > get whooping errors, and should validate carefully, but I've actually
> > been surprised several times by the results you can get without
> > specific parameterization. I'd like to point to UFF (not all
> > implementations though :-), VALBOND (not a complete force field, but
> > a very interesting addition to UFF), and the force fields in PCModel
> > and Spartan. There are others, but I don't have personal experience
> > with them.
> >
> > Per-Ola
> > --
> >
> > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > * Per-Ola Norrby, Associate Professor
> > * The Royal Danish School of Pharmacy, Dept. of Med. Chem.
> > * Universitetsparken 2, DK 2100 Copenhagen, Denmark
> > * Tel. +45-35306506, fax +45-35306040
> > * Email: peo -8 at 8- dfh.dk (preferred), peo -8 at 8-
compchem.dfh.dk
> > * WWW: http://compchem.dfh.dk/PeO/
> >
>
> --
> Isaac B. Bersuker
> Institute for Theoretical Chemistry
> Department of Chemistry & Biochemistry
> The University of Texas at Austin
> Austin, TX 78712, USA
> Ph: (512) 471-4671
> Fax: (512) 471-8696
> Email: bersuker -8 at 8- eeyore.cm.utexas.edu
>
> -= This is automatically added to each message by mailing script =-
> CHEMISTRY -8 at 8- ccl.net -- To Everybody | CHEMISTRY-REQUEST -8 at
8- ccl.net -- To Admins
> MAILSERV -8 at 8- ccl.net -- HELP CHEMISTRY or HELP SEARCH
> CHEMISTRY-SEARCH -8 at 8- ccl.net -- archive search | Gopher:
gopher.ccl.net 70
> Ftp: ftp.ccl.net | WWW: http://www.ccl.net/chemistry/ | Jan: jkl -8 at 8- ccl.net