[QE-users] [QE-user Stress tensor result difference between qe and vasp

[np_wangyi]

Hello everyone,
Recently, I did some calculation to compare the performace of qe and vasp. I find that the relative energies of pure dft of qe and vasp are quite consistent, and there are some differences between the forces on atoms. But as to the stress tensors, the differences are large. 
Below is the result data of one case (kbar)
==============================================
qe:
                             xx     xz     yx      xy 
ecutwfc_45Ry  11.83   5.92   9.02  -8.92
ecutwfc_50Ry  14.92   9.34  12.1   -8.75
ecutwfc_55Ry  13.16   7.61  10.33  -8.73
ecutwfc_60Ry  11.95   6.39   9.12  -8.73
ecutwfc_65Ry  12.03   6.47   9.21  -8.74
ecutwfc_70Ry  12.87   7.31  10.05  -8.74
ecutwfc_75Ry  13.89   8.36  11.08  -8.72
ecutwfc_80Ry  14.75   9.23  11.93  -8.71
==============================================
vasp:
Direction                       XX          YY              ZZ            XY      
ecutwfc_520ev       8.01175     1.70119     5.24923      -7.42910
ecutwfc_800ev       8.44879     1.99011     5.69489      -7.34710
==============================================
What I am curious about is the possiable reasons which make the result differences of the qe and vasp. Surely, psuedopotentials is one of the reasons. I expected the stress tensors are consistent like the relative energy results during the calculations, but it is not.
Happy to recevie any ideas about it. 
The vasp INCAR file and qe input file are attached. 


best,


Fang Liwen
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