[Pw_forum] a question about BORN Effective charges

[Paolo Giannozzi]

On Sat, Apr 22, 2017 at 7:33 PM, VineetKumar Pandey
<vineetkumar.pandey at students.iiserpune.ac.in> wrote:
> sir I performed phonon calculation for monolayer PbI2

QE version? serial or parallel execution? it is important to know how
you obtained your results.

> but I am getting born effective charges calculated by two ways
> (one is dF/dE and other is dP/du)

the dP/du results look ok (the two I atoms have almost the same
values, effective charges sum to almost 0), the dF/dE results don't.
There might be a problem in this specific case.

Paolo

>
>
>  Effective charges (d Force / dE) in cartesian axis
>
>            atom      1   I
>       Ex  (       -2.21984        0.00000        0.00000 )
>       Ey  (        0.00000       -2.21984        0.00000 )
>       Ez  (        0.00000        0.00000       -0.36016 )
>            atom      2   Pb
>       Ex  (        3.72748        0.00000        0.00000 )
>       Ey  (        0.00000        3.72748        0.00000 )
>       Ez  (        0.00000        0.00000        0.57697 )
>            atom      3   I
>       Ex  (       -1.93678        0.00000        0.00000 )
>       Ey  (        0.00000       -1.93678        0.00000 )
>       Ez  (        0.00000        0.00000       -0.36018 )
>
>           Effective charges (d P / du) in cartesian axis
>
>            atom      1   I
>       Px  (       -1.99748        0.00000        0.00000 )
>       Py  (        0.00000       -1.99748        0.00000 )
>       Pz  (        0.00000        0.00000       -0.30196 )
>            atom      2   Pb
>       Px  (        3.99223        0.00000        0.00000 )
>       Py  (        0.00000        3.99223        0.00000 )
>       Pz  (        0.00000        0.00000        0.60413 )
>            atom      3   I
>       Px  (       -1.99741        0.00000        0.00000 )
>       Py  (        0.00000       -1.99741        0.00000 )
>       Pz  (        0.00000        0.00000       -0.30197 )
>
>
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222