What is the meaning of stress in vasprun.xml?

[jun_yin2]

Hi,

After self consistent calculation, I execute

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grep stress OUTCAR

and it showed

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ISIF   =      2    stress and relaxation
   PSTRESS=    0.0 pullay stress
  external pressure =       -8.47 kB  Pullay stress =        0.00 kB

If I execute

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grep -A 3 stress vasprun.xml

, it showed

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 <varray name="stress" >
   <v>      -4.30818341      -1.82140260       0.28450240 </v>
   <v>      -1.82140258     -10.40841356      -0.47652276 </v>
   <v>       0.28450223      -0.47652268     -10.68000587 </v>

.
So I want to validate the RMSE in stress after the MLFF training. Does it mean I should use the latter stress to calculate the RMSE in stress? Also, which three stress tensors represent the x vector tensor? Hope you can help me. I will be very thankful.

[marie-therese.huebsch]

Hi,

I will try to help you.
Please upload your input files and main output files as a zip file (as required by the forum guidelines). Also, please clarify what you mean by validating RMSE.

Cheers,
Marie-Therese

[jun_yin2]

Hi,

Thanks for your help! I upload .zip containing DFT and MLFF calculation results. Both made self-consistent calculation with same POSCAR and POTCAR. I have deleted the ML_FF file in MLFF folder because its size is too large. In fact, I want to validate the accuracy of MLFF by checking the difference in energy, forces and stress between DFT and MLFF after SCF. So my question is: I know how to check energy and forces on each atom which are energy<sigma-0> and TOTAL-FORCE in OUTCAR. However, I do not know hoe to check stress difference between them. The only clue I found about stress is in vasprun.xml. Hope you could tell me the right answer.