Dear Dave,
I don't know if I get you very well.
About
the command geom=checkpoint, when this is states, gaussian find the geometry in
the checkpoint file independently of whether it would have been specified or not
in the input file.
Elsewhere, I do not understand what you are doing to overcome your problem. In
fact, I would like to precise to you that when using the key word
geom=checkpoint, it is better to add the command guess=read so that gaussian
will read guess orbitals in the checkpoint file. If this key word is missing,
the program would build default guess orbitals which are obviuosly different
from the previous ones. Therefore, it is normal to obtain different results with
and without the key word
guess=read specified. Finally, I want to mean
that, you have to add the key word guess=read which is appropriate to your
job.
Hope this would help.
Jean Jules FIFEN
University of
Douala,
Faculty of Science
Laboratoire de Physique
Fondamentale.
On 20 February 2011 22:19,
David M. Close closeda/
etsu.edu <owner-chemistry+/-ccl.net> wrote:
Sent to CCL by: "David M. Close" [closed++etsu.edu]
Last month I wrote a question to CCL about a problem with Gaussian .chk
files. I got a few replies about which keywords to use, but this I already
knew. I should have been more specific. I was trying to do a
frequency calculation on a previous SCRF calculation using G98. Apparently
this cannot be done. The calulation begin by reading the .chk file, but
then fails to open the information needed for the frequency calculation.
I gave up on this and switched to G03. This program does the same
SCRF calculation as G98 and gives the same answers. But there are still
problems with the frequency calculation if I do the following.
1) Run a geometry optimization.
2) Run a single point SCRF calculation using geom=checkpoint on the
geometry optimized xyz coordinates from part (1).
3) Do a frequency calculation on the SCRF job again using
geom=checkpoint.
Step three does the frequency calculation on the geometry from step (1),
which may be expected since I didn't reoptimize the structure in the SCRF
step. However I get a completely different answer if I elimate step (3)
and run step (2) with the combined SCRF and freq keywords in a single
step.
This procedure produces numbers that are not in agreement with calculations in
the literature.
Of course I may be doing something wrong here. For example I have
no idea how the command geom=checkpoint is used. Does anyone know if you
use a .chk file to do several calculations, which part is read by default if you
try to read it again?
Regards, Dave Close.
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Jules.