CCL: constrained geometry optmisation of molecular complexes



 Sent to CCL by: andras.borosy|,|givaudan.com
 Dear James,
 You may try semi-empirical methods as this has been done in the following
 articles:
 Timothy J. Giese, Edward C. Sherer, Christopher J. Cramer, and Darrin M.
 York, A Semiempirical Quantum Model for Hydrogen-Bonded
 Nucleic Acid Base Pairs, J. Chem. Theory Comput. (published in web in
 September 2005).
 E. NIKITINA, V. SULIMOV, V. ZAYETS, N. ZAITSEVA, International Journal of
 Quantum Chemistry, Vol 97, 747–763 (2004).
 Best wishes,
 Dr. András Borosy
 Seniour Scientist
 Delivery Systems, Fragrance Research
 Givaudan Schweiz AG
 Ueberlandstr. 138
 8600 Dübendorf
 Switzerland
 tel: + 41-1-8242164
 fax: +41-1-8242926
 e-mail: andras.borosy-#-givaudan.com
 owner-chemistry-#-ccl.net wrote on 10.10.2005 19:54:09:
 >
 > Sent to CCL by: Andreas Serr [serr/a\theorie.physik.uni-muenchen.de]
 > Dear James,
 >
 > sorry I cannot answer your questions, but I would like to make a
 > short comment on
 >
 > >  So far as I understand, HF
 > > methods, semi-empirical methods and most DFT functionals will not
 > > describe van-der-Waals forces (responsible for a good part of the
 > > non-binding interaction?) correctly.
 >
 > A standard HF or DFT calculation *does* incorporate Keesom and Debye
 > interactions (dipole-dipole, dipole-induced dipole) -- it will simply be
 > reflected in charge re-distributions of the molecules.
 >
 > You are right that they do *not* account for London (dispersion)
 interaction
 > (induced dipole-induced dipole).
 >
 > Depending on your system (mainly: magnitude of static dipole) either
 Keesom,
 > Debye or London interact. may dominate van-der-Waals forces.
 >
 > Sorry again, if it does not help for your question.
 >
 > Regards,
 > Andreas
 >
 >
 > Andreas Serr
 >
 > Biological Soft-Matter Theory
 > Sektion Physik - Ludwig-Maximilians-Universitaet
 > Theresienstr. 37, D-80333 Munich, Germany
 > tel: +49-(0)89-2180-4603 / fax: +49-(0)89-2180-4517
 > room no: 304 / e-mail: serr*theorie.physik.uni-muenchen.de
 > http://www.theorie.physik.uni-muenchen.de/biophysics/>;
 >