My Community

Hi,
Can you please help explain the stress tensor data in OUTCAR shown below.
I am confused in what does negative or positive signs in the second last and last lines mean. Also, how am I supposed to read stress and convert it to GPa from the data below?
Thank you.

FORCE on cell =-STRESS in cart. coord. units (eV):
Direction XX YY ZZ XY YZ ZX
--------------------------------------------------------------------------------------
Alpha Z 5220.60191 5220.60191 5220.60191
Ewald -17755.92843-17772.67388-17772.67388 0.00065 0.00067 -0.00233
Hartree 3488.06160 3488.06201 3488.06201 0.00003 0.00003 -0.00012
E(xc) -3478.70331 -3478.79443 -3478.79443 0.00000 0.00000 -0.00000
Local -975.67596 -959.09925 -959.09925 -0.00039 -0.00041 0.00141
n-local -1137.13980 -1136.44837 -1137.01367 0.00208 0.00199 0.00114
augment -543.95759 -543.66738 -543.66738 0.00001 0.00002 -0.00005
Kinetic 15180.08478 15181.06651 15183.67693 -0.02431 -0.01469 -0.00650
Fock 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000
-------------------------------------------------------------------------------------
Total -2.65681 0.06969 0.06969 -0.00000 0.00000 0.00000
in kB -3.00039 0.07870 0.07870 -0.00000 0.00000 0.00000
external pressure = -0.95 kB Pullay stress = 0.00 kB

Dear msalaken,

The data shows the various contributions to the stress tensor, for instance, the line marked with "Hartree" tells you how much the Hartree term in the Hamiltonian is contributing to the xx, yy, zz, xy, yz, and zx components.

After all individual contributions are displayed, you can see the total stress tensor (the sum of the previous lines for each component). However, this are not in standard units, so the next line gives you the same information, but now the data is shown in kB, i.e. a kilobar.

Finally you have the total pressure, which is defined as 1/3 of the trace of the stress tensor

You can find more information about the Pullay stress contribution on our wiki https://www.vasp.at/wiki/index.php/Ener ... lay_stress.

Hope this helps. Kind regards,
Pedro Melo