[CP2K-user] SCF convergence issues

Женя Елизарова zhene... at gmail.com
Thu Nov 5 16:20:20 UTC 2020

I see.
 Actually, I would like to know is it possible to run a single point energy 
calculation of the QM subsystem without the removal of the MM part, not in 
relation to the previous posts (in general)?

Best wishes,

четверг, 5 ноября 2020 г. в 19:08:44 UTC+3, Marcella Iannuzzi: 

> Dear Evgenia Elizarova
> Is this question related to the previous posts in this conversation? 
> If yes, what I meant is to remove all the MM part and just carry out a DFT 
> calculation of the QM part. 
> Regards
> Marcella
> On Thursday, November 5, 2020 at 3:29:42 PM UTC+1 zh... at gmail.com 
> wrote:
>> 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
>>>>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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