I have a model system composed of 6 small fragments (MW: 160-268). I am not able to converge the geometry.

The initial structure was minimized with a FF and when running in PSI4, I fix the all the heavy atoms. I’ve continued to lower the level of theory but it does not seem to be helping.

To be sure, when I say it’s not converging, I am not getting an error from PSI4, but rather I continue to see the energy drift slightly lower after every iteration – perhaps I am not waiting long enough, but it seems suspect from my past experience.

I’m wondering if there are other settings I should use?

On the forum, I did see mention of →

- Changing the ‘guess’ …

set basis_guess true

set guess huckel

set guess read

- Changing the number of grid points …

dft_spherical_points 434

dft_radial_points 85

dft_pruning_scheme robust

- And possible using uks vs rks …

But I’m unclear on the options – and welcome the help.

Thanks!