From owner-chemistry@ccl.net Mon Nov 3 15:19:00 2008 From: "errol lewars elewars%x%trentu.ca" To: CCL Subject: CCL:G: mail from Joshi Message-Id: <-38019-081103100933-21427-+By6ob9BbJYxn/Nh0GW5qw_-_server.ccl.net> X-Original-From: errol lewars Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=UTF-8; format=flowed Date: Mon, 03 Nov 2008 09:08:05 -0500 MIME-Version: 1.0 Sent to CCL by: errol lewars [elewars^^^trentu.ca] 2008 Nov 03 Are you starting from a good input geometry and using a good Hessian (I assume you are using the Berny algorithm)? A molecular mechanics geometry and Hessian, or an AM1 or PM3 geometry and Hessian, may help. E. Lewars ===== laxmikanth rao lkjoshiji,yahoo.com wrote: > Dear CCLers; Hi > > I am optimizing a molecule having 387 atoms (only C and H atoms) which > includes neatly 16 methyl groups as substitutions in G03w, and the > method is b3lyp/3-21g*. During the optimization the Maximum Force > and RMS Forces are sometimes converging, Maximum > Displacement and RMS Displacements are not converging and the > molecules energy is oscillating. I am using following keywords in > route section as > > %mem=1500mb > %nproc=4 > #p opt=(gdiis,maxcycle=200) b3lyp/3-21g* scf=maxcycle=500 > > Please give me suggestion > > Thanks in advance > > Joshi > > > ------------------------------------------------------------------------ > Add more friends to your messenger and enjoy! Invite them now. >