### Author Topic: aoforce + cosmo convergence  (Read 11148 times)

#### martijn

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• Posts: 63
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##### aoforce + cosmo convergence
« on: December 07, 2017, 05:30:08 PM »
Hi,

When combining aoforce with cosmo in 7.2.1 I encounter the following situation that I have never observed for gas phase frequency calculations:

COSMO cphf update
23       a      170        1.482021067048531D-05
b      170        7.672115628665743D-06

COSMO cphf update
24       a      170        1.482182443756061D-05
b      170        7.672115628665743D-06

COSMO cphf update
25       a      170        1.481440684000221D-05
b      170        7.672115628665743D-06

Warning! No convergence within  25 iterations.
Unless you have specified a very low \$escfiterlimit/\$forceiterlimit,
this is a reason to worry!

========================
internal module stack:
------------------------
force
========================

CPKS-Iteration did not converge !
force ended abnormally

Increasing the number of allowed iterations makes no difference whatsoever; the error/norm stays the same.

Does anybody have an idea what might be going on and if there's a parameter to play with in order to aid convergence? A NumForce + cosmo calculation on the same structure converges without any issues.

Thanks,

Martijn

#### uwe

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##### Re: aoforce + cosmo convergence
« Reply #1 on: December 08, 2017, 10:10:53 AM »
Hi Martijn,

the default convergence threshold is 10^-5, so you are more or less almost converged (1.48D-05). If the usual convergence enhancers like increasing DFT grid size (m3 to m4 or 4 or m5) and density convergence (\$denconv 1d-7) do not help, you probably hit the accuracy limit of the COSMO cavity derivative (holes in the cavity, very high charges on some small cavity patches, ...).

A pragmatic solution would be to restart escf (since you are already near convergence) and change the convergence settings for the CPKS iterations to \$rpaconv 4

Regards,

Uwe