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Dear Per-Ola Norrby:
I understand your point. But I really don't want to
compare wit X-rays, but to do a comparison
between calculated structures. Suppose, for
example, that I optimize the geometry of a molecule
with increasing basis set levels. Thus I have an STO-3G, 3-21G, 6-31G, 6-311G
optimized structures.
Then I calculate the
RMSD between each of the structures and that coming from the 6-311G
optimization (the
highest level in this example). I guess that the RMSD is going to decrease
from
a maximum value for
the STO-3G down to 0 corresponding to the 6-311G with itself.
Of course, the best match will be 0. But beside
this, can we take a RMSD value (what I call the
threshold value in my previous message) and
consider it closely enough to the best match ?
In order words, that the structure optimized with,
say 6-31G, will be almost as good as 6-311G ?
I know that the example I has given is a very
simple and moreover abstract one. That is why I
asked my question in the CCL hoping that the
experience of the members with different
molecular geometry optimizations will help me. Of
course, I understand the problem in terms
of listings of bonds and angles.
Thanks in advance
Daniel
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Dr. Daniel Glossman-Mitnik Centro de Investigación en Materiales Avanzados (CIMAV) LAQUICOM - Laboratorio de Química Computacional Miguel de Cervantes 120 - Comp. Ind. Chihuahua Chihuahua, Chih. 31109 - MEXICO Tel.: (52) 614 4391151 FAX: (52) 614 4391112 E-mail: daniel.glossman{at}cimav.edu.mx glossman{at}hotmail.com dglossman{at}yahoo.com **********************************************************************
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