[Pw_forum] Should I scrap the nonanalytic part of DM in electroded thin films?

[Serge Nakhmanson]

Dear All,

A small question to those of you with expertise in
phonon calculations of ionic crystals.

I understand that in bulk calculations the dynamical
matrices at small q are split into analytic and
nonanalytic parts, with the latter accounting for the
effects of macroscopic electric field. However, if
we want to study phonons in a model representing an
electroded thin film instead of a bulk crystal (i.e.,
the electrodes are not explicitly included in such a
calculation), we should assume that such an electric
field will be screened out by the free charges and
its influence onto ionic vibrations should not be
considered.

I am under an impression that to achieve this in pwscf
I need to block the calls to nonanal(...) subroutine
in dynmat and matdyn, while leaving everything else
intact. Would this work out or could it possibly be not
as trivial as I imagine it?

Would appreciate your comments,

Serge

-- 
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  Serge M. Nakhmanson               phone: (630) 252-5205
  Assistant Scientist                 fax: (630) 252-4798
  MSD-212, Rm. C-224
  Argonne National Laboratory
  9700 S. Cass Ave.
  Argonne, IL 60439
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