From owner-chemistry@ccl.net Mon Feb 21 15:09:01 2011 From: "Jean Jules FIFEN julesfifen*gmail.com" To: CCL Subject: CCL:G: Gaussian .chk files Message-Id: <-43993-110221150809-19862-E9O266xzYOANkHnwB4ppQg**server.ccl.net> X-Original-From: Jean Jules FIFEN Content-Type: multipart/alternative; boundary=bcaec53f9683d932eb049cd06b76 Date: Mon, 21 Feb 2011 21:08:03 +0100 MIME-Version: 1.0 Sent to CCL by: Jean Jules FIFEN [julesfifen-*-gmail.com] --bcaec53f9683d932eb049cd06b76 Content-Type: text/plain; charset=ISO-8859-1 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.> > > -- Jules. --bcaec53f9683d932eb049cd06b76 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Dear Dave,
I don't know if I get you very well.
= About the command geom=3Dcheckpoint, when this is states, gaussian find the= geometry in the checkpoint file independently of whether it would have bee= n 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= =3Dcheckpoint, it is better to add the command guess=3Dread so that gaussia= n will read guess orbitals in the checkpoint file. If this key word is miss= ing, the program would build default guess orbitals which are obviuosly dif= ferent from the previous ones. Therefore, it is normal to obtain different = results with and without the key word guess=3Dread specified. Finall= y, I want to mean that, you have to add the key word guess=3Dread which is = appropriate to your job.

Hope this would help.


Jean Jules FIFEN
University of Doua= la,
Faculty of Science
Laboratoire de Physique Fondamentale.

<= br>
On 20 February 2011 22:19, David M. Close clo= seda/etsu.edu <owner-chemistry+/-ccl.net> = wrote:

Sent to CCL by: "David M. Close" [closed++etsu.edu]
=A0Last month I wrote a question to CCL about a problem with Gaussian .chk= files. =A0I got a few replies about which keywords to use, but this I alre= ady knew. =A0I should have been more specific. =A0I was trying to do a freq= uency calculation on a previous SCRF calculation using G98. =A0Apparently t= his cannot be done. =A0The calulation begin by reading the .chk file, but t= hen fails to open the information needed for the frequency calculation.
=A0I gave up on this and switched to G03. =A0This program does the same SC= RF calculation as G98 and gives the same answers. =A0But there are still pr= oblems with the frequency calculation if I do the following.
=A01) Run a geometry optimization.
=A02) Run a single point SCRF calculation using geom=3Dcheckpoint on the = =A0 =A0 =A0geometry optimized xyz coordinates from part (1).
=A03) Do a frequency calculation on the SCRF job again using geom=3Dcheckp= oint.

=A0Step 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. =A0However I get a completely different answer if I elimate step= (3) and =A0run step (2) with the combined SCRF and freq keywords in a sing= le step.
This procedure produces numbers that are not in agreement with calculations= in the literature.
=A0Of course I may be doing something wrong here. =A0For example I have no= idea how the command geom=3Dcheckpoint is used. =A0Does 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?

=A0Regards, Dave Close.



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--
Jules.
--bcaec53f9683d932eb049cd06b76--