[QE-users] Regarding U in self-consistant and site dependent

[Anish Das]

Dear experts,

I am interested in calculating Hubbard-U in self consistent and and site
dependent manner as i am dealing with local point defect and expecting
different charged states near the defect. First, I activated the U
calculation machinaries by applying very small U value (10^-8).Then I
perturbed the inequivalent open-shell Hubbard sites and got 1st shot of U
values (for different sites). Then I am supposed to use new values of U and
again go for the 2nd shot U calculation.

Now my questions are.

1) Should i relax the structure with U values calculated from 1st shot then
go for the 2nd shot? Or i just simply plugin the new U, do SCF and go for
the 2nd shot U-calculation. Dr. Iurii Timrov mentioned to relax the
structure everytime with new U values in his paper. But my structure is
large and has 52 Hubbard sites (159 total atoms).

2) As i mentioned earlier that my system has 52 inequivalent Hubbard sites,
so 1st i perturbed the all sites and get the 1st shot of U. Then i relaxed
the structure with new U's. Now after the relaxation when i check the
inequivalent Hubbard sites for 2nd shot U calculation (by hp.x), it is now
showing i have 48 Hubbard sites (instead of 52) to be perturbed. My
question is, should i need to perturb the 52 sites (determined during the
1st shot) or 48 sites (determined during 2nd shot calculation)?

Thanking you
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