From chemistry-request %-% at %-% server.ccl.net Fri Dec 20 04:45:11 2002 Received: from gate3.oss.akzonobel.nl ([192.87.3.7]) by server.ccl.net (8.11.6/8.11.0) with ESMTP id gBK9jAi22239 for ; Fri, 20 Dec 2002 04:45:10 -0500 Received: (from fwmaster ":at:" localhost) by gate3.oss.akzonobel.nl (8.9.3a/8.6.12) id KAA22873 for ; Fri, 20 Dec 2002 10:45:10 +0100 (MET) Received: by gate3.oss.akzonobel.nl via smap (V1.3) id sma013213; Fri, 20 Dec 02 10:37:04 +0100 Received: by triton.oss.intra with Internet Mail Service (5.5.2653.19) id ; Fri, 20 Dec 2002 10:37:04 +0100 Message-ID: <639D20177889D41198A600508BAD3CA1039AD2DD%!at!%capella3.oss.akzonobel.nl> From: "Lommerse, J.P.M. (Jos)" To: "'chemistry # - at - # ccl.net'" Cc: "Vuuren, M. van (Marlous)" Subject: Constrained geometry optimisation with GAUSSIAN98 Date: Fri, 20 Dec 2002 10:37:00 +0100 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2653.19) Content-Type: text/plain; charset="iso-8859-1" Hello, I am trying to optimize the geometry of small organic molecules while keeping fixed all dihedral angles at certain values around rotatable bonds. Whatever optimization procedure (Berny, Steep, etc.) I apply, or start conformation I choose, the optimization fails to arrive at a true local minimum, viz. the resulting geometry always contains one or more imaginary frequencies. Does anybody know how to get to a true local minimum while applying these dihedral angle constraints? Here's an simple problem molecule example com-file for GAUSSIAN98 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %chk=pdb35.chk # rhf/PM3 Molecule pdb35 (1isi_NCA_1) 0 1 N 6.3300 42.5360 90.0450 C 5.1180 41.9260 90.5820 C 3.9970 42.7130 90.9900 C 4.1850 44.1520 90.8210 C 5.3590 44.7550 90.2990 C 6.4330 43.9350 89.9100 C 2.6760 42.1220 91.5670 O 1.7720 42.8950 91.8870 N 2.5360 40.8370 91.7060 H 5.0663 40.8412 90.6744 H 3.3664 44.8083 91.1165 H 5.4271 45.8385 90.2010 H 7.3421 44.3799 89.5054 H 3.3010 40.2032 91.4339 H 1.6602 40.4528 92.0883 --Link1-- %chk=pdb35.chk #T rhf/PM3 geom=(checkpoint,modify) opt=modredundant * * A * * * A * * * * A * 3 7 * F ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Thanks a lot, Jos Lommerse jos.lommerse ^%at%^ organon.com Dr Ir Jos Lommerse, Research Scientist Molecular Design & Informatics, N.V. Organon Molenstraat 110, PO Box 20, 5340 BH Oss, THE NETHERLANDS -------------------------------------------------------------------- This message, including attached files, may contain confidential information and is intended only for the use by the individual and/or the entity to which it is addressed. Any unauthorized use, dissemination of, or copying of the information contained herein is not allowed and may lead to irreparable harm and damage for which you may be held liable. If you receive this message in error or if it is intended for someone else please notify the sender by returning this e-mail immediately and delete the message. --------------------------------------------------------------------