From chemistry-request@ccl.net Thu Jul 1 20:09:47 2004 Received: from brass.metals.hope.edu (brass.metals.hope.edu [198.110.98.36]) by server.ccl.net (8.12.8/8.12.8) with SMTP id i6219k8b011045 for ; Thu, 1 Jul 2004 20:09:46 -0500 Received: from hope.edu ([198.110.98.17]) by brass.metals.hope.edu (SAVSMTP 3.1.1.32) with SMTP id M2004070121124229122 ; Thu, 01 Jul 2004 21:12:42 -0400 Received: from [198.110.101.2] (polik*at*hope.edu) by hope.edu; Thu, 1 Jul 2004 21:12:58 -0400 X-WM-Posted-At: hope.edu; Thu, 1 Jul 04 21:12:58 -0400 Message-Id: <5.2.0.9.2.20040701210918.02627eb8*at*webmail.hope.edu> X-Sender: polik*at*webmail.hope.edu (Unverified) X-Mailer: QUALCOMM Windows Eudora Version 5.2.0.9 Date: Thu, 01 Jul 2004 21:14:49 -0400 To: Carsten Detering , chemistry*at*ccl.net From: "William F. Polik" Subject: CCL:gaussian03 optimization to transition state In-Reply-To: <40E45989.9090503*at*u.washington.edu> Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="=====================_431109562==.ALT" X-Spam-Status: No, hits=3.0 required=7.5 tests=HTML_MESSAGE,NO_RDNS2 autolearn=no version=2.61 X-Spam-Checker-Version: SpamAssassin 2.61 (1.212.2.1-2003-12-09-exp) on servernd.ccl.net --=====================_431109562==.ALT Content-Type: text/plain; charset="us-ascii"; format=flowed Carsten, The success of a transition state optimization depends on how close you start to the optimized geometry. The optimized geometries are likely to be different in a MOPAC semi-empirical calculation than in a B3LYP/6-31g* calculation. However, you might better your odds at converging by trying B3LYP/6-31g* OPT=(TS,CalcFC,NoEigenTest) which requests that Gaussian calculate, rather than approximate, the force constants used in the optimization and not initially fail if more than one negative frequency is found. Will Polik At 02:35 PM 7/1/2004, Carsten Detering wrote: > I would like to optimize a complex involving a bifurcated hydrogen bond > between three nitrogen atoms (trimethylamine and triazen) to a saddle > point (which I know exists from previous Mopac calculations). Taking this > header line in the input file > >B3LYP/6-31g* POpt=(Saddle=1) nosymmetry test > >the optimization finishes with an error > >optimization stopped > --wrong number of Negative eigenvalues: Desired= 1 Actual= 2 > --Flag reset to prevent archiving > >Then I get, at the bottom, the typical proverb that you see only when a >calculation has successfully finished, and then > >Could anybody make some suggestions how to fix this? > >Thanks a lot in advance, > >Carsten ================================ Dr. William F. Polik Hofma Professor of Chemistry Department of Chemistry Hope College 35 East 12th Street Holland, MI 49422-9000 USA polik*at*hope.edu http://www.chem.hope.edu/~polik tel: (616) 395-7639 fax: (616) 395-7118 ================================ --=====================_431109562==.ALT Content-Type: text/html; charset="us-ascii" Carsten,

The success of a transition state optimization depends on how close you start to the optimized geometry. The optimized geometries are likely to be different in a MOPAC semi-empirical calculation than in a B3LYP/6-31g* calculation. However, you might better your odds at converging by trying

B3LYP/6-31g* OPT=(TS,CalcFC,NoEigenTest)

which requests that Gaussian calculate, rather than approximate, the force constants used in the optimization and not initially fail if more than one negative frequency is found.

Will Polik

At 02:35 PM 7/1/2004, Carsten Detering wrote:

I would like to optimize a complex involving a bifurcated hydrogen bond between three nitrogen atoms (trimethylamine and triazen) to a saddle point (which I know exists from previous Mopac calculations). Taking this header line in the input file

B3LYP/6-31g* POpt=(Saddle=1) nosymmetry test

the optimization finishes with an error

optimization stopped
--wrong number of Negative eigenvalues: Desired= 1 Actual= 2
--Flag reset to prevent archiving

Then I get, at the bottom, the typical proverb that you see only when a calculation has successfully finished, and then

Could anybody make some suggestions how to fix this?

Thanks a lot in advance,

Carsten

================================
Dr. William F. Polik
Hofma Professor of Chemistry

Department of Chemistry
Hope College
35 East 12th Street
Holland, MI 49422-9000
USA

polik*at*hope.edu
http://www.chem.hope.edu/~polik
tel: (616) 395-7639
fax: (616) 395-7118
================================
--=====================_431109562==.ALT--