CCL:G: mail from Joshi

 Sent to CCL by: errol lewars [elewars^^^]
 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, 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
 #p opt=(gdiis,maxcycle=200) b3lyp/3-21g* scf=maxcycle=500
Please give me suggestion Thanks in advance Joshi
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