From owner-chemistry@ccl.net Sun Nov 13 18:47:01 2011
From: "Brian Salter-Duke brian.james.duke_._gmail.com" <owner-chemistry{}server.ccl.net>
To: CCL
Subject: CCL: Convergence During Frequency Analysis
Message-Id: <-45877-111113181747-25551-qY+GdqawXwxgKC8UGqbjBQ{}server.ccl.net>
X-Original-From: Brian Salter-Duke <brian.james.duke]|[gmail.com>
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Date: Mon, 14 Nov 2011 10:10:28 +1100
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Sent to CCL by: Brian Salter-Duke [brian.james.duke=gmail.com]
On Sun, Nov 13, 2011 at 03:33:11PM -0600, Josh Marell mare0051-#-umn.edu wrote:
> Hello,
> 
> I am optimizing a geometry at the m062x/6-31+g(d,p) level, and then I
> perform a frequency analysis.  During the optimization step (and utilizing
> opt=verytight), I ensure that I am getting full convergence and see:
> 
> Maximum Force            0.000000     0.000002     YES
>  RMS     Force            0.000000     0.000001     YES
>  Maximum Displacement     0.000005     0.000006     YES
>  RMS     Displacement     0.000001     0.000004     YES
> 
> However, then I carry out a frequency analysis using the following route
> section:
> # m062x/6-31+g(d,p) freq integral(ultrafinegrid) scrf=check geom=checkpoint
> 
> And at the end of the output file for the frequency analysis, it indicates
> in this specific case that none of the criteria have converged (this is
> after the line that specifies the axes has been restored to the original
> set)
> 
>          Item               Value     Threshold  Converged?
>  Maximum Force            0.024599     0.000450     NO
>  RMS     Force            0.005725     0.000300     NO
>  Maximum Displacement     0.311758     0.001800     NO
>  RMS     Displacement     0.083739     0.001200     NO
>  Predicted change in Energy=-4.741844D-03
>  GradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGrad

Is the energy in the freq run identical to the energy in the last step
of the optimisation run?

Did you have "integral(ultrafinegrid)" and scrf in the opt run?

> Is this telling me the results of the frequency analysis are not reliable?

It is certainly telling you something is wrong.

Brian.
 
>  I guess I'm unclear why the geometry that converged with verytight
> requirement is now not converging during the frequency job (assuming I'm
> understanding the implication of the above correctly).
> 
> Thank you,
> 
> Josh

-- 
   Brian Salter-Duke (Brian Duke)   Brian.Salter-Duke^_^monash.edu
                    Adjunct Associate Professor
            Monash Institute of Pharmaceutical Sciences
      Monash University Parkville Campus, VIC 3052, Australia