[CP2K-user] SCF convergence issues

[Женя Елизарова]

Dear  Marcella Iannuzzi

I've just started to explore opportunities of the cp2k package. I've done 
some tutorials about single-point calculations of ethane molecule, QM/MM 
simulations, and some more. I am very interested in single point energy 
calculation for the QM part of the system. As I understood, I have to 
define the force_eval section (method - quickstep), and also I have to 
define subsections: dft, subsys, qmmm. Did I understand correctly? Also, i 
have some questions.
Do I have to define the MM subsection? In subsys section, I should define 
the whole system?  How to define for which part of the system run a single 
point calculation?
 Could you help me, please?

Best wishes, 
Evgenia Elizarova
понедельник, 2 ноября 2020 г. в 11:55:28 UTC+3, Marcella Iannuzzi: 

> Dear Ryan Rogers
>
> There is apparently a problem with the conservation of the charge on the 
> QM grid. 
>
> Did you try to run a single point energy calculation for the QM part alone?
> Kind regards
> Marcella
>
> On Thursday, October 29, 2020 at 7:11:42 PM UTC+1 r... at nyu.edu wrote:
>
>> 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/20201105/dd36f13d/attachment.htm>