Dear all,
I found out that it was impossible de make a phonon calculation without
calculating the Born effective charge in a semi-conductor even if we set
epsil = .false.
This is due to the routine prepare_q.f90 that is called inside do_phonon.f90
In the routine there is
IF ( lgamma ) THEN
!
IF ( .NOT. lgauss ) THEN
!
! ... in the case of an insulator at q=0 one has to calculate
! ... the dielectric constant and the Born eff. charges
! ... the other flags depend on input
!
epsil = .TRUE.
zeu = .TRUE.
zue = .TRUE.
This means that if we compute q=Gamma and if we do not have
gaussian-smearing (i.e. an semi-cond or insulator), then epsil is
automatically set to TRUE.
I know that physically one should have such LO/TO splitting but the user
should be able to choose.
Maybe this forcing could be reported in the input variable ? or simply put
the default value to .TRUE. instead of false and not enforcing that rule?
What do you think?
Best,
Samuel Ponce,
Department of Materials, University of Oxford
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