[CP2K-user] SCF convergence issues

[Ryan Rogers]

I might add that I have not been able to identify any obvious problems with 
the configurations (e.g. overlapping or too close atoms, etc.) when I 
encounter these errors. 

On Monday, October 26, 2020 at 4:07:46 PM UTC-5 Ryan Rogers wrote:

> Dear CP2K community, 
>
> I am having issues in DFT QM/MM force calculations on molecular crystals 
> of paracetamol (acetaminophen). I am describing here the two problems I 
> most often experience. I am currently unable to identify the cause or any 
> pattern in the problems I encounter. The root of the problems could be 
> something other than what I identify below; I am pointing out the 
> problematic features in the output that are most obviously to me. All input 
> and output files are included. 
>
> *1. Total energy falls into "hole" and never converges. 
> (CP2K_problemTotalE_conf_0636.tar.gz)*
> Personal experience tells me to expect a "Total energy" for these systems 
> on the order of -2,000 (Hartree) and a "Hartree energy" on the order of 
> +2,000 (Hartree).
> In these jobs, I find an initial "Hartree energy" on the order of >-10,000 
> (Hartree), which appears to send the SCF wavefunction optimization down a 
> path of non-convergence, in which the "Total energy" can easily become on 
> the order of -100,000 (Hartree) before I kill the job.
>
> *2. Total charge density on grids grows too large. 
> (CP2K_problemEGrids_conf_0623.tar.gz)*
> In these jobs, the Total energy looks reasonable, and the Convergence 
> looks promising in the few SCF cycles of steps. 
> However, the total Change never drops below my threshold, and eventually 
> the "Total charge density on r-space/g-space grids" becomes much too large.
>
> My configurations are extracted from MD trajectories, so the atoms have 
> perturbations from their perfect crystal positions. One confusing 
> observation is that very similar QM/MM configurations selected from other 
> frames of the same trajectory often have no problems.
> My configurations are constructed from a cluster of several molecules in 
> the QM region with usually another layer usually 1-2 molecules thick making 
> up the MM region. (In the attached sample images, the size of the stick 
> molecules alludes to a larger/smaller basis set used, while the MM atoms 
> are denoted as points.) Because I am not including integer numbers of unit 
> cells, I am not using PBC. 
>
> Any advice about both/either problem will be greatly appreciated!
>
> Sincerely,
> Ryan Rogers
> r... at nyu.edu
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20201029/f7f36f63/attachment.htm>