[CP2K-user] [CP2K:17456] Different values of stress tensor from FORCE_EVAL and MOTION sections duing MD

[Abhishek Sharma]

Dear CP2K users,

I am trying to monitor the stress tensor in my ab initio MD simulation in 
NPT ensemble using CP2K version 7.1. I wrote two print sections, one in 
FORCE_EVAL section (to print stress file) as
...
  &PRINT
    &FORCES             ON
      FILENAME          =forces
    &END FORCES
    &STRESS_TENSOR      ON
        FILENAME        =stress
    &END STRESS_TENSOR
  &END PRINT
  STRESS_TENSOR         ANALYTICAL

and another in PRINT of MOTION section (to get pressure file)
...
        &STRESS
            &EACH
                MD 1
            &END
            FILENAME pressure
        &END STRESS

After running the job , I got following output in the stress file:
 STRESS TENSOR [GPa]
            X               Y               Z
  X       0.00106044     -0.00003023     -0.00393423
  Y      -0.00003023      0.01251158      0.00014630
  Z      -0.00393423      0.00014630      0.00717328
  1/3 Trace(stress tensor):   6.91510096E-03
  Det(stress tensor)      :  -9.84767286E-08
 EIGENVECTORS AND EIGENVALUES OF THE STRESS TENSOR
         -0.00086519      0.00909269      0.01251781

          0.89817098     -0.43935160     -0.01609565
         -0.00277868     -0.04228259      0.99910183
          0.43963755      0.89731954      0.03919782
  
==============================================================================
   Stress Tensor Components (GPW/GAPW)
                                                1/3 Trace           
Determinant
   Kinetic Energy Stress                       1.22833622           
 0.02852337
   Basis Overlap Stress                        0.30458944           
 0.01186246
   ES + XC Stress                          -1736.32537740     
 ****************
   vdW correction (ff) Stress                 -0.00517761           
-0.00000010
   Local Pseudopotential/Core Stress          -0.88167272           
-0.56052030
   Nonlocal Pseudopotential Stress             2.92262879           
20.96427765
   Exact Exchange Stress                      -0.00000000           
-0.00000000
   Sum of Parts Stress                     -1732.75667328     
 ****************
   Total Stress                                0.00785295           
-0.00000014
  
==============================================================================
 STRESS TENSOR [GPa]
            X               Y               Z
  X      -0.05130320      0.02112443     -0.15716038
  Y       0.02112443      0.07439468     -0.03381687
  Z      -0.15716038     -0.03381687      0.04697689
  1/3 Trace(stress tensor):   2.33561233E-02
  Det(stress tensor)      :  -1.75455374E-03

while in pressure file I got following output
 
#   Step   Time [fs]            xx [bar]            xy [bar]            xz 
[bar]            yx [bar]            yy [bar]            yz [bar]           
 zx [bar]            zy [bar]            zz [bar]
       0       0.000     2291.7724124002       -7.8261381151     
 -11.6256055821       -7.8261381151     2225.2853884787      190.2135354318 
     -11.6256055821      190.2135354318     2617.3106021379
       1       0.500     1721.2682620818      206.1262199908   
 -1539.1469767016      206.1262199908     2804.1547381410     
-143.2394364947    -1539.1469767016     -143.2394364947     2958.6420055205

Both files have values different units (GPa in stress file and bar in 
pressure file). After converting values to same unit (say bar) the xx 
stress value 10.60 bar (0.00106044 GPa) does not match with the value of  
2291.77 bar in the pressure file. Can you please help me to understand this 
? Am I doing something wrong in my input file. The print output of cell 
vectors from the MOTION section is following:

#   Step   Time [fs]       Ax [Angstrom]       Ay [Angstrom]       Az 
[Angstrom]       Bx [Angstrom]       By [Angstrom]       Bz [Angstrom]     
  Cx [Angstrom]       Cy [Angstrom]       Cz [Angstrom]      Volume 
[Angstrom^3]
       0       0.000       16.9813194275        0.0000000000       
 0.0000000000        0.0009342941       17.1132431030        0.0000000000   
    -0.0392083935        0.0056124185       17.0369434357         
 4951.0285723949
       1       0.500       16.9878393880       -0.0026240361       
 0.0088682212       -0.0017097687       17.1090517191        0.0016270059   
    -0.0303270449        0.0072363688       17.0367331490         
 4951.6596469487

Many thanks ,
Abhishek



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