CCL:G: geometry optimization convergence problem

["施良" <shiliang(0)mail.ustc.edu.cn>]

 Sent to CCL by: "=?gb2312?B?yqnBvA==?=" [shiliang]~[mail.ustc.edu.cn]
 Dear Alexander:
 Below methods might be helpful:
 1. Change initial geometry according to the oscilliation situation by using
 Gaussview or other software.
 2. Considering your PES might be flat, IOp(1/8=N) might take effect. (See
 Gaussian.com)
 As for GDIIS, I have not used it but Gaussian03 online manual writes:
 Recommemded
 for use with ... molecules with flat potential energy surfaces.
 Hope some method will work. Good luck!
 Liang Shi
 ÔÚÄúµÄÀ´ÐÅÖÐÔø¾­Ìáµ½:
 >From: "Alexander Hoepker achoepker]*[gmail.com"
 <owner-chemistry]|[ccl.net>
 >Reply-To: "CCL Subscribers" <chemistry]|[ccl.net>
 >To: "Shi, Liang " <shiliang]|[mail.ustc.edu.cn>
 >Subject: CCL:G: geometry optimization convergence problem
 >Date:Thu, 16 Apr 2009 09:08:53 -0400
 >
 >Dear CCL community,
 >I am having difficulty with a particular geometry optimization using
 >B3LYPlevel of theory using a
 >6-31G(d) basis set while constraining a bondlength using the
 >ModRedundantkeyword in Gaussian. The geometry sequence energies drop
 >nicely but then
 >plateau at an average value while oscillating endlessly without ever
 >converging. The Maximum and RMS Forces have converged whereas the
 >Displacements have not. Would GDIIS help with this?
 >Any suggestions would be very much appreciated.
 >
 >Thanks,
 >
 >Alexander Hoepker
 >Cornell University
 >Department of Chemistry and Chemical Biology