[Pw_forum] Finite electric field (smearing , DFT+U, and total energy)

[Paolo Giannozzi]

On Fri, May 22, 2015 at 9:51 AM, Mostafa Youssef <myoussef at mit.edu> wrote:

 Is there a fundamental reason for why smearing should not be used with
> Berry phase calculations, or is it possible to modify PWscf to accept
> smearing?
>

the latter you said. Unfortunately there are many pieces of code on Berry
phases, electric fields, orbital magnetization, that have been written
having in mind spinless insulators with all bands filled only, and never
generalized. However, it seems to me, at a quick glance to
PW/src/bp_c_phase.f90, that you can compute Berry phases with smearing, as
long as the final result is insulating.

>
> (2) I recall Prof. Giannozzi in this mailing list mentioned that DFT+U is
> not tested with Berry phase calculations.
>

I don't remember anything about DFT+U and Berry phases, but I don't see any
obvious reasons why these two options shouldn't work together.

 The total energies that PWscf outputs in finite electric field
> calculations are in fact electric enthalpies.  One could check that the (
> Harris-Foulkes estimate   +  (total dipole x field)) is the what PWscf
> prints as the total energy. I think it would be nice to designate this
> output  as the electric enthalpy especially that this will be consistent
> with what PWscf prints out for calculations under pressure.


I'll leave this point to people interested in calculations under electric
field

Paolo
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