[Pw_forum] lelfield and lberry

[alan chen]

Dear PWSCF users,
      I am now running a calculation of strained STO  and try to calculate
its spontaneous polarization based on Berry phase method. I try two
different ways:
1) run a self-consistent calculation turning on lelfield=.true. and set
efield=0.0
2) first run a self-consistent calculation and  then run a
non-self-consistent calculation turning on lberry=.true.
Are these two method equivalent? When I try these two methods on the same
system, method 1) works well but method 2) fails because "probably because
G_par is NOT a reciprocal lattice vector".

I notice that (in the version 4.0) in the two subroutines bp_c_phase.f90 and
c_phase_field.f90 the definition of gpar are different by a factor
DBLE(nppstr)/DBLE(nppstr-1). But I think these two gpar should be the same
thing?

I just want to ask whether the option lberry is fully tested and compatible
with 'lelfield = .true.'.
Thank you very much for your help.

Hanghui Chen
Department of Physics
Yale University
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