[CP2K-user] [CP2K:21503] Re: System exploded in NPT-F simulations

[Zhuoran Long]

Dear Prof. Iannuzzi,

Thank you so much for the suggestions. CELL, STRESS, kinetic and potential 
energy of the barostat all oscillates around some values and I guess that 
means fine. However I noticed that the kinetic energies of the thermostats 
keep increases, both for the one applied on the atoms and the one coupled 
to the barostat. 
I made some tests including 
(a) remove the "TYPE SAME_AS_PARTICLE" so that the TIMECON of the 
thermostat coupled to the barostat becomes 200 as specified in the input
(b) from (a), change the TIMECON of the barostat to 2000
(c) from (b), change the TIMESTEP to 0.2
and none of them seem to fix the problem. 
I would really appreciate it if you could please provide any additional 
suggestions.

Thank you!
Zhuoran 

The following plots were from the initial simulations but all the tests 
(a-c) show similar trends. 
[image: t300_cell.png][image: t300_stress.png][image: t300_e.png]
On Tuesday, May 27, 2025 at 5:02:27 AM UTC-4 Marcella Iannuzzi wrote:

>
> Dear Zhuoran
>
> Have you also monitored the CELL , the STRESS and the energy and 
> temperature of the barostat?
> When they change too fast, it is difficult for the dynamics to recover. 
> In this case you can try to rescale the temperature of the barostat and 
> reduce the time step.
> Regards
> Marcella
>
> On Saturday, May 24, 2025 at 10:38:05 AM UTC+2 zlo... at umd.edu wrote:
>
>> Dear all,
>>
>> I am testing NPT simulations on the tutorial water system 
>> <https://www.cp2k.org/exercises:2018_ethz_mmm:h2o_md>. I'm including the 
>> following changes to the input file in the tutorial example:
>>
>> &FORCE_EVAL
>>     STRESS_TENSOR ANALYTICAL
>>     ...
>> &END FORCE_EVAL
>> ...
>> &MOTION
>>   &MD
>>     ENSEMBLE NPT_I
>>     STEPS 200000
>>     TIMESTEP 1.0
>>     TEMPERATURE 300
>>     COMVEL_TOL 1.0E-10
>>     &BAROSTAT
>>       PRESSURE 1.01325 #[bar]
>>       TIMECON 1000
>>       VIRIAL XYZ
>>       &THERMOSTAT
>>         TYPE SAME_AS_PARTICLE
>>         &CSVR
>>           TIMECON 200
>>         &END CSVR
>>       &END THERMOSTAT
>>     &END BAROSTAT
>>     &THERMOSTAT
>>       TYPE CSVR
>>       REGION MASSIVE
>>       &CSVR
>>         TIMECON 200
>>       &END CSVR
>>     &END THERMOSTAT
>>     ...
>>   &END MD
>>   ...
>> &END MOTION
>>
>> The Cons Qty in the .ener file converged after about 20 ps. However. when 
>> I perform the same simulation from scratch in the NPT-F ensemble (by 
>> changing the NPT-I to NPT-F), the Cons Qty kept increasing and exploded 
>> after about 80 ps (please see the plot below, so are the kinetic energy and 
>> potential energy). I will need the NPT-F in future for a tetragonal 
>> covalent organic framework system. Could someone please let me know if I 
>> had any wrong or missing parameters? 
>> And a relevant question, while I set the time constant to be 200 for the 
>> CSVR thermostat of the barostat, the corresponding TIMECON in the restart 
>> file has a value of ~9.6755. Is that relevant to my question? I'm using the 
>> version 2024.2. 
>>
>> And helps and discussions are greatly appreciated.
>> Zhuoran
>> [image: t300.png]
>>
>

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