From owner-chemistry@ccl.net Tue Aug 26 08:04:01 2008 From: "Pascal Boulet pascal.boulet#univ-provence.fr" To: CCL Subject: CCL:G: End of a frequency job Message-Id: <-37625-080825152140-12045-0Z7+jbSqWtt9gqWMQqMaaA-x-server.ccl.net> X-Original-From: Pascal Boulet Content-Type: multipart/alternative; boundary="------------010105060909070605070607" Date: Mon, 25 Aug 2008 20:48:11 +0200 MIME-Version: 1.0 Sent to CCL by: Pascal Boulet [pascal.boulet],[univ-provence.fr] This is a multi-part message in MIME format. --------------010105060909070605070607 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit hello, It sounds strange to me that some people are using different basis sets for optimization and frequency calculations. In principle, the geometry is no longer at the minimum of the PES when the BS is changed, and in the case of frequency jobs, one can get imaginary frequencies. Pascal Close, David M. CLOSED^mail.etsu.edu wrote: > Sent to CCL by: "Close, David M." [CLOSED__mail.etsu.edu] > Yes, that is exactly right. As a check you could try a frequency calc. > using the same basis set. Usually 3 out of 4 of the "yes" are ok. For > some reason the third "yes" is sometimes a "no". I don't know why. > Now a more basic question. If you are taking a course on doing > calculations, you are always told you must use the same basis sets in > frequency calculations as on the original optimizations. But people > seem to be getting away from this are very large calculations. If it > takes a week to do an optimization, it might take 3-4 weeks to do a > frequency calculation. So people are now using smaller basis sets to do > faster frequency calcs. I do not happen to know if this leads to > problems. I do know that Berny Schlegel warned about this some time > ago, but I do not know the current thinking on this. > > > -----Original Message----- > >> From: owner-chemistry ~~ ccl.net [mailto:owner-chemistry ~~ ccl.net] >> > Sent: Monday, August 25, 2008 11:29 AM > To: Close, David M. > Subject: CCL:G: End of a frequency job > > > Sent to CCL by: Orlin Blajiev [Orlin.Blajiev,vub.ac.be] > David, Alcides, > > > > Thanks for the info. I guess G03 reports the geometry as non-converged > > because I use different BS in Opt and Freq. > > Best regards, > Orlin > > > Alcides Simao alsimao[#]gmail.com wrote: > >> Orlin: >> >> This is a routine check from GAUSSIAN, made after *all* frequency >> jobs. You can safely discart it. Gaussian will always do that, even if >> > > >> you don't flag the 'OPT' option. >> >> Best, >> >> Alcides >> > > > -- Dr. Pascal Boulet, Computational Chemist University of Provence Laboratoire Chimie Provence, UMR6264 Centre Saint-Jerome, case MADIREL F-13397 MARSEILLE Cedex 20, France Tel. +33 (0) 491 63 71 17 Fax. +33 (0) 491 63 71 11 courriel: pascal.boulet|,|univ-provence.fr http://www.lc-provence.fr http://allos.up.univ-mrs.fr/boulet --------------010105060909070605070607 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit hello,

It sounds strange to me that some people are using different basis sets for optimization and frequency calculations. In principle, the geometry is no longer at the minimum of the PES when the BS is changed, and in the case of frequency jobs, one can get imaginary frequencies.

Pascal

Close, David M. CLOSED^mail.etsu.edu wrote:

Sent to CCL by: "Close, David M." [CLOSED__mail.etsu.edu]
Yes, that is exactly right.  As a check you could try a frequency calc.
using the same basis set.  Usually 3 out of 4 of the "yes" are ok.  For
some reason the third "yes" is sometimes a "no".  I don't know why.
Now a more basic question.  If you are taking a course on doing
calculations, you are always told you must use the same basis sets in
frequency calculations as on the original optimizations.  But people
seem to be getting away from this are very large calculations.  If it
takes a week to do an optimization, it might take 3-4 weeks to do a
frequency calculation.  So people are now using smaller basis sets to do
faster frequency calcs.  I do not happen to know if this leads to
problems.  I do know that Berny Schlegel warned about this some time
ago, but I do not know the current thinking on this.


-----Original Message-----

From: owner-chemistry ~~ ccl.net [mailto:owner-chemistry ~~ ccl.net]

Sent: Monday, August 25, 2008 11:29 AM
To: Close, David M.
Subject: CCL:G: End of a frequency job

Sent to CCL by: Orlin Blajiev [Orlin.Blajiev,vub.ac.be]
David, Alcides,

Thanks for the info. I guess  G03 reports the geometry as  non-converged

because I use different  BS in Opt and  Freq.

Best regards,
Orlin

Alcides Simao alsimao[#]gmail.com wrote:

Orlin:

This is a routine check from GAUSSIAN, made after *all* frequency 
jobs. You can safely discart it. Gaussian will always do that, even if

you don't flag the 'OPT' option.

Best,

Alcides

-- 
Dr. Pascal Boulet, Computational Chemist
University of Provence
Laboratoire Chimie Provence, UMR6264
Centre Saint-Jerome, case MADIREL
F-13397 MARSEILLE Cedex 20, France
Tel. +33 (0) 491 63 71 17 Fax. +33 (0) 491 63 71 11
courriel: pascal.boulet|,|univ-provence.fr
http://www.lc-provence.fr
http://allos.up.univ-mrs.fr/boulet

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