aoforce + cosmo convergence

[martijn]

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]

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