Subject: G94 and G98

From: Emadeddin Tajkhorshid <[email-masked]>
Date: Thu, 15 Apr 1999 21:02:36 -0700

Dear CCL

I have experienced something using geometry optimization in G94 and G98
that I would like to check with you. I started from a G94-optimized set
of  coordinates for glycine. Using a DFT method (B3LYP/6-31G**), on the
same platform (IBM/SP2) I started the same job in G94 and G98. These two
jobs, while having the same optimization criteria (Default values) and
the same starting geometries (and I suppose the same initial guess?)
give different results. In one case the geometry is optimized and in the
other case, the job does not meet the 'Maximum displacement' and 'RMS
displacement' criteria after the first cycle. Examination of the energy
also shows that we have different values after the first SCF. 

Although the differences in this case are not very large, I would like
to know why they happen. If I am not mistaken there are some
modifications with respect to the optimizer in G98, but I think in the
case of this example, the difference is happening at the level of
wavefunction. 

Did anybody else experience such differences at the wavefunction or
geometry level? If so, how large are they? 

**********************G94 job*************************************
First SCF:

 SCF Done:  E(RB+HF-LYP) =  -284.437033067     A.U. after   15 cycles
             Convg  =     .4529D-08             -V/T =  2.0089
             S**2   =    .0000
 KE= 2.819396660737D+02 PE=-1.026794554909D+03 EE= 2.802029338205D+02

:::::
         Item               Value     Threshold  Converged?
 Maximum Force             .000028      .000450     YES
 RMS     Force             .000009      .000300     YES
 Maximum Displacement      .000293      .001800     YES
 RMS     Displacement      .000108      .001200     YES
 Predicted change in Energy=-1.479922D-08
******************************************************************

**********************G98 job*************************************
First SCF:

 SCF Done:  E(RB+HF-LYP) =  -284.437035418     A.U. after   15 cycles
             Convg  =     .4595D-08             -V/T =  2.0089
             S**2   =    .0000
 KE= 2.819396670445D+02 PE=-1.026794557138D+03 EE= 2.802029327275D+02

::::
 Maximum Force             .000028      .000450     YES
 RMS     Force             .000012      .000300     YES
 Maximum Displacement      .004390      .001800     NO 
 RMS     Displacement      .001377      .001200     NO 
 Predicted change in Energy=-7.549560D-08
******************************************************************

-- 
Emad
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E. Tajkhorshid, Ph.D. 
German Cancer Research Center; DKFZ             Tel: +49 6221 42 2340
Dept. Molecular Biophysics (H0200)              FAX: +49 6221 42 2333
P.O.Box 101949            http://genome.dkfz-heidelberg.de/users/emad
69009 Heidelberg, Germany     Email: [email-masked]
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