From chp1aa@surrey.ac.uk Mon Apr 11 09:56:47 1994 Received: from mail-server.surrey.ac.uk for chp1aa@surrey.ac.uk by www.ccl.net (8.6.4/930601.1506) id JAA21516; Mon, 11 Apr 1994 09:10:36 -0400 Received: from central.surrey.ac.uk by mail-server.surrey.ac.uk with SMTP using (PP) id <29210-0@mail-server.surrey.ac.uk>; Mon, 11 Apr 1994 14:10:25 +0100 Received: by central.surrey.ac.uk (1.37.109.8/16.2) id AA24031; Mon, 11 Apr 1994 14:10:23 +0100 From: Mr Andrew D Allen Message-Id: <9404111310.AA24031@central.surrey.ac.uk> Subject: CCL:Problem with SCF convergence in AMPAC To: chemistry@ccl.net Date: Mon, 11 Apr 94 14:10:23 BST Mailer: Elm [revision: 70.85] I am running AMPAC v2.1 and have run into problems with SCF convergence. I have a large, ~60 atoms, molecule which converges OK if carry out a geometry optimisation on all coordinates. The problem arises when I try to constrain the optimisation by flaging some of the bonds, angle and torsions to not be optimised. Has anyone experienced this problem with Semi-emp, or QM methods in general, and has anyone any possible ways to overcome the problem. I would like to avoid doing a full geometry optimisation for the molecule due to its size. Andy. -- ################################################################################ Structural and Computation Chemistry Group__________chp1aa@uk.ac.surrey - JANET. Department of Chemistry_____________________________phone__+44(483)-300800-2632. University of Surrey________________________________fax_________+44(483)-300803. Guildford, Surrey, GU2 5XH, UK______________________ftp____________131.227.110.2 ################################################################################