CCL: Convergence During Frequency Analysis

From: Brian Salter-Duke <brian.james.duke]|[gmail.com>
Subject: CCL: Convergence During Frequency Analysis
Date: Mon, 14 Nov 2011 10:10:28 +1100
 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