[CP2K:4620] Re: energy drift in NPT MD simulation

Bonakala Satyanarayana satyanaray... at gmail.com
Fri Sep 20 06:41:05 CEST 2013


Dear Seitsonen,
             Thank you for your reply.
1) I performed NVT simulation with same input, what I have enclosed. It ran
well. These are the converged energy values:
 ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):
 -7812.764025944994501
 ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):
 -7812.749474147461115
 ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):
 -7812.722559495744463
 ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):
 -7812.689485930668525
 ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):
 -7812.657322690376532
 ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):
 -7812.631945457889742
 ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):
 -7812.616274832782437
 ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):
 -7812.609299468986137
2) I have taken cut-off as per literature (Elucidating the Breathing of the
Metal–Organic Framework MIL-53(Sc) with ab Initio Molecular Dynamics
Simulations and in Situ X-ray Powder Diffraction Experiments, Duren et al.,
JACS). Here, they have tested for  MIL MOFs and reported optimum cut-off is
350 Ry.

Dear Hutter,

1) Yes, my system is stable in NVT simulation

2) Det( stress tensor) values are
  Det(stress tensor)      :  -7.84528984E-04
  Det(stress tensor)      :  -1.66559235E-02
  Det(stress tensor)      :  -1.44160312E+00
  Det(stress tensor)      :   2.03287049E+02
  Det(stress tensor)      :  -4.82023324E+03
  Det(stress tensor)      :   4.36251297E+07
  BAROSTAT temperature is increasing:
  BAROSTAT TEMP[K]             =          0.250067070500E+03
  BAROSTAT TEMP[K]             =          0.407906043312E+05
  BAROSTAT TEMP[K]             =          0.373591928441E+06
  BAROSTAT TEMP[K]             =          0.458891514234E+08

3) SCF convergence is smooth. I enclosed the convergence vs steps


Thank you

B.Satyanarayana, Ph. D
Molecular modeling lab
JNCASR
Bangalore


On Thu, Sep 19, 2013 at 2:34 PM, Ari Paavo Seitsonen <
ari.p.s... at gmail.com> wrote:

> Dear Satyanarayana B,
>
>   Indeed the energy does not "drift", it explodes. What did happen in an
> NVT simulation with otherwise the same input, did the simulation work fine?
>
>   To me the cut-off energy of 350 Ry looks low, even with the PBE
> functional (smoother than BLYP); did you test that it is sufficient?
>
>     Greetings from Zurich,
>
>        apsi
>
> PS Does some one know, are the methods in &XC_GRID ... &END XC_GRID
> consistent with an NPT simulation?
>
>
> 2013/9/19 Matt W <MattWa... at gmail.com>
>
>> Hi,
>>
>> well your system is clearly exploding. Your cell_ref parameters look
>> inconsistent with your actual cell - maybe the stress tensor is very bad!
>>
>>   &SUBSYS
>>
>>>     &CELL
>>>       ABC 21.8620 16.2099 43.6020
>>>       ALPHA_BETA_GAMMA 90.0 92.7540 90.0
>>>      &CELL_REF
>>>       ABC 22.8620 17.2099 44.6020
>>>       ALPHA_BETA_GAMMA 90.0 126.0 90.0
>>>      &END CELL_REF
>>>
>>>     &END CELL
>>>
>>>  --
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>
>
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>   Physikalisch-Chemisches Institut der Universität Zürich
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