[Pw_forum] Berry phase electric field calculations with empty bands
Alexander.Urban at chemie.uni-erlangen.de
Tue Nov 1 16:43:04 CET 2011
Thank you for your response, Paolo Giannozzi.
On 11/01/2011 04:11 PM, Paolo Giannozzi wrote:
> based on my little knowledge of the subject, I would say (1) yes,
> (2) likely no.
That is what I thought...
> It should be relatively straightforward to generalized
> the current algorithms to work even in presence of unoccupied
> bands (it is sufficient to consider the correct weight), but
> i) it hasn't been done (or it hasn't been completed), and
> ii) it must be done in a proper way, avoiding to increase
> the complexity of the code.
I do consider to introduce the necessary modifications.
Maybe someone more familiar with the PWSCF code could point me into the
- The electric enthalpy SCF wavefunctions are wrong (with empty bands)
because the electric polarization P is wrong.
- The reason for the error in P is that the sums in the computation
of P in `c_phase_field()' run over all nbnd bands where it should
only be the occupied ones (i.e. the occupation numbers have to be used
- The only subroutine that has to be modified is `c_phase_field()'.
If this reasoning is correct, I would take a closer look at
`c_phase_field()' and estimate the effort to introduce the changes.
Alexander Urban (PhD student)
Interdisciplinary Center for Molecular Materials (ICMM)
Computer Chemistry Center (CCC)
University of Erlangen-Nuremberg
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