Can CP2K fixed part of atoms when perform CI-NEB?

J. Ye jingyu... at gmail.com
Tue Nov 8 17:12:41 CET 2016


I have another question. The default value for CONVERGENCE_CONTROL 
<https://manual.cp2k.org/cp2k-4_1-branch/CP2K_INPUT/MOTION/BAND/CONVERGENCE_CONTROL.html> for 
BAND optimization is very difficult to converge. I was curious is why the 
criterias for BAND optimization is so high? What is the reasonable 
criteria?   
    &CONVERGENCE_CONTROL
      MAX_DR 0.0002
      MAX_FORCE 0.00045
      RMS_DR 0.0001
      RMS_FORCE 0.0003
    &END CONVERGENCE_CONTROL



On Tuesday, November 8, 2016 at 9:32:49 AM UTC-6, J. Ye wrote:
>
> Hi Matthias, 
>
> I am working on a catalyst material that has metal nanoparticles supported 
> on a porous material.  This porous material which is a big system that has 
> about 600 atoms, however the catalytic reaction process only on the metal 
> clusters. We want to study the effect of the pore size on the catalytic 
> reaction. So I want to perform a periodic calculations and compare with 
> cluster model. If the barriers are similar, then I could perform for 
> cluster model instead. 
>
> Your suggestion is peroform QM/MM? 
>
> What's the difference between DIIS and MD? Why DIIS is more efficient? Do 
> you have any books or papers recommend for us to read? 
>
> Thanks very much!
>
> Best regards,
>  
> J. Ye
>
> On Tuesday, November 8, 2016 at 2:12:42 AM UTC-6, Matthias Krack wrote:
>>
>> Hi
>>
>> do you have any special reason to use the OPT_TYPE MD? Otherwise I 
>> suggest to try the default OPT_TYPE DIIS which should be much more 
>> efficient. Moreover, if you want to fix some atoms only because of the 
>> computational cost caused by the large size of your system then there will 
>> be most likely not much benefit doing so, because the forces for all atoms 
>> are calculated anyway and then set to zero for the fixed atoms afterwards. 
>> You should rather check if fixing atoms is really needed as a boundary for 
>> a realistic modelling of the reaction you are interested in.
>>
>> Best regards
>>
>> Matthias
>>
>> On Tuesday, 8 November 2016 07:01:18 UTC+1, J. Ye wrote:
>>>
>>>  Hi Fabio, 
>>>
>>> I indeed included both "ALIGN_FRAMES FALSE" and "ROTATE_FRAMES FALSE" in 
>>> my input(Please see the attachment). But I still found the atoms moves. The 
>>> methods we use are different. I don't know how does this affect the fixed 
>>> atoms. Do you have any idea? 
>>>
>>> I have tested your input. Atom 1 and 3 indeed do not move. I also tried 
>>> to switch TI-NEB to CI-NEB, the atoms are not move. So this should not be 
>>> affected by BAND_TYPE. 
>>>
>>> Can any expert of CP2K give us some hints on this problem? 
>>>
>>> Thanks very much!
>>> Best,
>>>
>>> J. Ye
>>>
>>> On Monday, November 7, 2016 at 2:02:05 PM UTC-6, elb... at gmail.com 
>>> wrote:
>>>>
>>>> Hello J. Ye!
>>>>
>>>> Yes, I have checked. If you use only the constraint flag, indeed the 
>>>> fixed atoms move for the other images. But if you include both 
>>>> "ALIGN_FRAMES FALSE" and "ROTATE_FRAMES FALSE" flags in the BAND section, 
>>>> that does not happen anymore, at least in the calculations I have performed 
>>>> so far. Check for example the NEB input attached to this e-mail. It is very 
>>>> simple and it runs very fast (it has no meaning, it is just an example), 
>>>> but you can check that atoms 1 and 3, that are asked to be fixed, do not 
>>>> move for all NEB images. Let me know if you get the same behavior as me!
>>>>
>>>> All the best!
>>>>
>>>
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