[Q-e-developers] Finite electric field (saw tooth) implementation details required (UNCLASSIFIED)

[Paolo Giannozzi]

On Feb 15, 2011, at 15:50 , Balu, Radhakrishnan (Cont, ARL/WMRD) wrote:
>
> is it feasible to change the pw code to support a more general  
> potential with
> a constant region ( a pulse shaped potential)?

I think it is. I am not sure that it will make a difference whether  
the potential
is a sawtooth or it is constant in some region of space, though: the  
region
where the electric field changes sign has to be in the vacuum region  
anyway.

The implementation of electric fields in PWscf is somewhat confusing.  
First
of all there is an implementation of macroscopic electrc fields based  
on the
modern theory of polarization (Berry phases) that shouldn't be  
confused with
the sawtooth+supercell approach. Second, the latter is implemented in a
somewhat confusing way. Note that it includes the case of "dipolar  
correction"
for surfaces, which needs to be performed self-consistently, so it  
looks more
complex than it actually is.

> If so could you please provide me [...] pointers to the relevant  
> portion of the
> code so that I can attempt to change the code for my purpose.


PW/add_efield.f90

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