From owner-nwchem-users@emsl.pnl.gov Wed Apr 11 08:41:31 2007 Received: from odyssey.emsl.pnl.gov (localhost [127.0.0.1]) by odyssey.emsl.pnl.gov (8.13.8/8.13.8) with ESMTP id l3BFfTTB016241 for ; Wed, 11 Apr 2007 08:41:30 -0700 (PDT) Received: (from majordom@localhost) by odyssey.emsl.pnl.gov (8.13.8/8.13.8/Submit) id l3BFfTH2016240 for nwchem-users-outgoing-0915; Wed, 11 Apr 2007 08:41:29 -0700 (PDT) X-Authentication-Warning: odyssey.emsl.pnl.gov: majordom set sender to owner-nwchem-users@emsl.pnl.gov using -f X-Ironport-SG: OK_Domains X-Ironport-SBRS: 3.5 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AgAAACyeHEaGeQBAh2dsb2JhbACDCIx7AgEIDio X-IronPort-AV: i="4.14,395,1170662400"; d="scan'208,217"; a="17612934:sNHT38613078" X-MimeOLE: Produced By Microsoft Exchange V6.5 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01C77C4F.DDE9CE78" Subject: [NWCHEM] getting rid of negative frequencies Date: Wed, 11 Apr 2007 08:41:25 -0700 Message-ID: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: getting rid of negative frequencies Thread-Index: Acd8T90qjMF/tvkvQbCj0I1LHwSxxw== From: "Clark, Aurora" To: Sender: owner-nwchem-users@emsl.pnl.gov Precedence: bulk This is a multi-part message in MIME format. ------_=_NextPart_001_01C77C4F.DDE9CE78 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable Hi; =20 I have been doing some geometry optimizations of systems with fairly flat PES. Anyway, I have the driver convergence for optimization set to tight but I keep on getting one or more imaginary vibrations from the subsequent frequency calculation. I have been taking the Geometry after 100.0% step for the most negative mode and restarting the geometry optimization, however this doesn't seem to really be helping the driver find a true minimum. As a relatively new user to nwchem I was wondering if anyone had any other suggestions....I had thought about using the INHESS flag and reading in the Cartesian Hessian from the previous frequency calculation, however I am unable to find an example of how the Cartesian Hessian should be formatted in the input file? Alternatively it looks like geometry optimization with stepper might be a better option? =20 Any advice would be most appreciated :-) =20 Aurora =20 =20 =20 Aurora Clark Assistant Professor of Chemistry=20 Washington State University Pullman, WA 99164 Ph. (509)-335-3362 =20 ------_=_NextPart_001_01C77C4F.DDE9CE78 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable

Hi;

 

I have been doing some =
geometry optimizations of systems with fairly flat PES. Anyway, I have =
the driver convergence for optimization set to tight but I keep on =
getting one or more imaginary vibrations from the subsequent frequency =
calculation. I have been taking the  Geometry after  100.0% =
step for the most negative mode and restarting the geometry =
optimization, however this doesn’t seem to really be helping the =
driver find a true minimum. As a relatively new user to nwchem I was =
wondering if anyone had any other suggestions….I had thought about =
using the INHESS flag and reading in the Cartesian Hessian from the =
previous frequency calculation, however I am unable to find an example =
of how the Cartesian Hessian should be formatted in the input file? =
Alternatively it looks like geometry optimization with stepper might be =
a better option?
 
Any advice would be most =
appreciated J
 
Aurora

 

 

 

Aurora = Clark

Assistant Professor of Chemistry =

Washington State University

Pullman<= i>, WA = 99164=

Ph. = (509)-335-3362

 

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