[CP2K-user] [CP2K:21497] System exploded in NPT-F simulations

[Zhuoran Long]

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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