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

[Matthias Krack]

Hi

the default values might be tight, but these defaults should be considered 
like all other default values only as a first guess or proposal which has 
to be adapted to the actual application.

Best regards

Matthias

On Tuesday, 8 November 2016 17:12:41 UTC+1, J. Ye wrote:
>
> 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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