TURBOMOLE Users Forum
TURBOMOLE Modules => Aoforce and Numforce => Topic started by: martijn 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 1.482021067048531D05
b 170 7.672115628665743D06
COSMO cphf update
24 a 170 1.482182443756061D05
b 170 7.672115628665743D06
COSMO cphf update
25 a 170 1.481440684000221D05
b 170 7.672115628665743D06
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
========================
CPKSIteration 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

Hi Martijn,
the default convergence threshold is 10^5, so you are more or less almost converged (1.48D05). If the usual convergence enhancers like increasing DFT grid size (m3 to m4 or 4 or m5) and density convergence ($denconv 1d7) 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