[Q-e-developers] Fwd: Question about the old bug in finite electric field

[Paolo Giannozzi]

Begin forwarded message:

> From: Andrei Malashevich <andreim at berkeley.edu>
> Date: April 11, 2012 1:13:49  GMT+02:00
> To: Paolo Giannozzi <giannozz at democritos.it>
> Subject: Question about the old bug in finite electric field
>
> Dear Paolo,
>
> I have a question regarding the following bug that was fixed some time
> ago
>
> http://qe-forge.org/cgi-bin/cvstrac/q-e/chngview?cn=8140
>
> There was a minor change in PW/electrons.f90 where one line of the  
> code
> was replaced with something else (lines 991-992 of the current SVN
> version):
>
> !el_pol_cart(i)=el_pol_cart(i)+transform_el(j,i)*el_pol(j)
> el_pol_cart(i)=el_pol_cart(i)+at(i,j)*el_pol(j)/(dsqrt(at(1,j)**2.d0
> +at(2,j)**2.d0+at(3,j)**2.d0))
>
> The meaning of the new (corrected) version seems clear to me. On the
> other hand, I don't quite understand what transform_el matrix is. The
> reason I am asking about transform_el is that it appears few lines  
> below
> (line 1026 in the current SVN version) in an analogous expression as
> above
>
> el_pol_acc_cart(i)=el_pol_acc_cart(i)+transform_el(j,i)*el_pol_acc(j)
>
> Should this line be changed in the same way it was done above? If not,
> can you please explain the meaning of transform_el to me?
>
> I really appreciate your help on this.
>
> Thank you,
> Andrei

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Paolo Giannozzi, Dept of Chemistry&Physics&Environment,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222