[QE-users] a problem related to the electric field calculations

[Mostafa Youssef]

Dear Samare,


You are performing 'scf' calculation for Ti-doped Fe2O3 under electric
field.  This gives only the electron's response to the field.  If you are
interested in ions response (and in fact the ion-electron response) , you
may need to use 'relax'. Of course make sure to relax the zero field
Ti-doped hematite first before you start electric field calculations.

For plain PBE for Ti, you may end up with a metallic solution. Ti wants to
be in oxidation state +4 and the leftover electron may (or may not) spread
over the whole cell causing metallic solution. In this case of metallic
solution, electric field calculations will not converge.  You may check the
state of the last electron by plotting DOS  or visualizing the defect state
in 3D.

Also, the field is large. Add it gradually as I described in my previous
post.

I never used the pseudos you are using. But the ones here:
https://www.materialscloud.org/discover/sssp/table/efficiency
are usually very good. Although Fe pseudo is very computationally intensive.

If you change the occupations to 'smearing' and add a tiny smearing (0.004
Ry), this can accelerate the convergence. Again this is after you make sure
that the last electron in Ti-doped hematite is not leading to a metallic
solution.

Hope this helps


Regards,
Mostafa
AUC
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