[DFTB-Plus-User] How to interpret Pressure

rsaha at icredd.hokudai.ac.jp rsaha at icredd.hokudai.ac.jp
Tue Apr 27 07:09:06 CEST 2021


Hello All,

I am doing an optimisation using PBC. The pressure is fluctuating from +
ve to -ve (the values are shown below). The optimized geometry has a 
pressure of '-0.393159E+06 Pa'.
I am interested to know about the Pressure values in each step and how 
to interpret them?
 

***  Geometry step: 4233, Lattice step: 8

 iSCC Total electronic   Diff electronic      SCC error    
    1   -0.80272425E+03    0.00000000E+00    0.56829621E-06
 
Total Energy:                     -799.8611912841 H       -21765.3304 eV
Total Mermin free energy:         -799.8611912841 H       -21765.3304  
eV
Volume:                              0.465323E+06 au^3   0.689538E+05 A^
3
Pressure:                           -0.271457E-07 au    -0.798655E+06 Pa
Maximal force component:             0.414549E-04
Maximal Lattice force component:     0.220811E-03 au
>> Charges saved for restart in charges.bin

------------------------------------------------------------------------
--------

***  Geometry step: 4234, Lattice step: 9

 iSCC Total electronic   Diff electronic      SCC error    
    1   -0.80272866E+03    0.00000000E+00    0.48898886E-04
    2   -0.80272866E+03   -0.20990001E-08    0.37070024E-04
    3   -0.80272866E+03   -0.73657702E-09    0.78422156E-05
    4   -0.80272866E+03   -0.23169378E-09    0.28803937E-05
    5   -0.80272866E+03   -0.73896445E-11    0.84029493E-06
 
Total Energy:                     -799.8611911242 H       -21765.3304 eV
Total Mermin free energy:         -799.8611911242 H       -21765.3304  
eV
Volume:                              0.465283E+06 au^3   0.689478E+05 A^
3
Pressure:                            0.483587E-08 au     0.142276E+06 Pa
Maximal force component:             0.641709E-04
Maximal Lattice force component:     0.289920E-03 au
>> Charges saved for restart in charges.bin

------------------------------------------------------------------------
--------

***  Geometry step: 4235, Lattice step: 9

 iSCC Total electronic   Diff electronic      SCC error    
    1   -0.80272866E+03    0.00000000E+00    0.84029493E-06
 
Total Energy:                     -799.8611911242 H       -21765.3304 eV
Total Mermin free energy:         -799.8611911242 H       -21765.3304  
eV
Volume:                              0.465283E+06 au^3   0.689478E+05 A^
3
Pressure:                            0.483587E-08 au     0.142276E+06 Pa
Maximal force component:             0.641709E-04
Maximal Lattice force component:     0.289920E-03 au
>> Charges saved for restart in charges.bin

------------------------------------------------------------------------
--------

***  Geometry step: 4236, Lattice step: 10

 iSCC Total electronic   Diff electronic      SCC error    
    1   -0.80272615E+03    0.00000000E+00    0.28110365E-04
    2   -0.80272615E+03   -0.67404926E-09    0.21297410E-04
    3   -0.80272615E+03   -0.23862867E-09    0.44801872E-05
    4   -0.80272615E+03   -0.74464879E-10    0.16272333E-05
    5   -0.80272615E+03   -0.25011104E-11    0.46484779E-06
 
Total Energy:                     -799.8611914971 H       -21765.3304 eV
Total Mermin free energy:         -799.8611914971 H       -21765.3304  
eV
Volume:                              0.465306E+06 au^3   0.689512E+05 A^
3
Pressure:                           -0.133632E-07 au    -0.393159E+06 Pa
Maximal force component:             0.498087E-04
Maximal Lattice force component:     0.417916E-06 au
>> Charges saved for restart in charges.bin

------------------------------------------------------------------------
--------

***  Geometry step: 4237, Lattice step: 10

 iSCC Total electronic   Diff electronic      SCC error    
    1   -0.80272615E+03    0.00000000E+00    0.46484779E-06
 
Total Energy:                     -799.8611914971 H       -21765.3304 eV
Total Mermin free energy:         -799.8611914971 H       -21765.3304  
eV
Volume:                              0.465306E+06 au^3   0.689512E+05 A^
3
Pressure:                           -0.133632E-07 au    -0.393159E+06 Pa
Maximal force component:             0.498087E-04
Maximal Lattice force component:     0.417916E-06 au
>> Charges saved for restart in charges.bin

Geometry converged


Thank you for your time and consideration.
Please give your suggestion(s).
Regards
Ranajit






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