From owner-nwchem-users@emsl.pnl.gov Fri May 7 12:59:23 2004 Received: from odyssey.emsl.pnl.gov (localhost [127.0.0.1]) by odyssey.emsl.pnl.gov (8.12.10/8.12.10) with ESMTP id i47JxNjO025064 for ; Fri, 7 May 2004 12:59:23 -0700 (PDT) Received: (from majordom@localhost) by odyssey.emsl.pnl.gov (8.12.10/8.12.10/Submit) id i47JxNad025063 for nwchem-users-outgoing; Fri, 7 May 2004 12:59:23 -0700 (PDT) Date: Fri, 07 May 2004 14:59:30 -0500 From: "David A. Dixon" Subject: RE: NWChem analytical and numerical 2nd derivatives In-reply-to: <5132851F-A05E-11D8-AAB7-000A95C9C668@bancorp.ru> To: "'Grigory Shamov'" , nwchem-users@emsl.pnl.gov Reply-to: dadixon@bama.ua.edu Message-id: <000e01c4346d$d2473c60$eb70a082@pnl.gov> Organization: The University of Alabama MIME-version: 1.0 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1409 X-Mailer: Microsoft Outlook, Build 10.0.3416 Content-type: text/plain; charset=US-ASCII Content-transfer-encoding: 7bit Importance: Normal X-Priority: 3 (Normal) X-MSMail-priority: Normal Sender: owner-nwchem-users@emsl.pnl.gov Precedence: bulk Why would you want to do finite differences if analytic methods are available? It is cheaper to do analytic and the frequencies are better. Dave Dixon -----Original Message----- From: owner-nwchem-users@emsl.pnl.gov [mailto:owner-nwchem-users@emsl.pnl.gov] On Behalf Of Grigory Shamov Sent: Friday, May 07, 2004 2:40 PM To: nwchem-users@emsl.pnl.gov Subject: NWChem analytical and numerical 2nd derivatives Hi All, Could someone please advice me, how could one choose the method of calculation of the energy 2nd derivatives? NWChem manual says that the program selects method (either analytical or finite differences) of the hessian calculation using information of its availability for the given level of theory. But what if you need to enforce finite difference hessian calculation even with analytical hessians are available? Thank you! -- Best regards, Gregory Shamov, postdoc Department of Chemistry University of Manitoba mailto: shamov@cc.umanitoba.ca