[Pw_forum] about wannier center
Andrea Ferretti
ferretti.andrea at unimore.it
Sun Sep 2 16:27:25 CEST 2007
Hi,
On Sat, 1 Sep 2007, Wei Zhou wrote:
> thank both of you for your helpful discuss above, I just to learn to
> calcuation *maximally localized wannier function, and meet some new
> question.i have done scf and nscf calculation without problem, but i donnot
> know how to choose the win_max and froz_max ,is it accrossling to band
> calculation results?
this is question which goes deep in the definition of the disentanglement
procedure; first of all, refer to the original paper by
Souza, Marzari and Vanderbilt, PRB 65, 035109 (2001), if you didn't
already
as a brief summary:
win_max and win_min are the input flags defining the bloch states
entering the disentanglement procedure (all the eigenstates
win_min < eps_nk < win_max are taken in the starting bloch manyfold)
froz_min and froz_max define a second (or inner) energy window, which
should be contained in the previous one: all the eigenstates falling
inside this frozen window will be directly taken into the wannier
manyfold (subset of the bloch manyfold which will be used later on to
localize maxim. loc. WFs)
note that the choice of these parameters may be quite sensible on the
final results
the largest the energy window (win_min, win_max) you take, the better
invariant spread you obtain since you are enlarging the number of dregrees
of freedom of the problem... of course, it will take longer
the smaller the frozen_window you take, the less constrained your
minimization is, and the better minimization you get (but take care,
the constrain is useful to take the lowest states as much similar to
the origial ones (nscf calculation) as possible)
the basic ideas about how to chose these windows are stated in the
original PRB paper above... some tricks can also be found in
http://www.wannier-transport.org/PDF/want_manual.pdf
> when I do disentangle calculation or wannier
> calculation ,it always appear error result as below
>
> *** from PE : 0
> *** in routine : card_wannier_centers
> *** error msg. : reading line I
> *** error code : 1
> *** aborting ***
>
> it seems that wannier center is wrong ,for my system is sodium , I take
> the s p orbits into accout, then I set the center as follow
> atomic 1 0 1
> atomic 1 -1 1
> atomic 1 -1 2
there is a problem with the parameters you provided
the syntax is:
atomic atomic_index ang_mom_L_number ang_mom_M number
the first integer is the index defining the atom you want to consider...
the second integer is the L angular momentum quantum number which should
be >= 0 (and hence the error given by the code, since you set -1), the
third integer is M ( -L,..., +L)
to get an sp manyfold, use eg
> atomic 1 0 0
> atomic 1 1 0
> atomic 1 1 1
> Is it right ? for wannier calculation ,I am not sure how to control the
> input date for "wannier_Na.in",would you help me .give some important
> suggestion?
>
> another question is when I calcuate MLWF of the structure with 54
> atoms calculated from molecular dyanmics , the symmetry is P1 ,then how I
> should choose which atom as the wannier center so that the internal
> atomphere is represent
if I understand correctly,
at the moment there is no way of imposing a certain symmetry of the final
subset of WFs... especially when you perform a disentanglement procedure.
typically the symmetry (or some lower symmetry, if the case) is only
recovered during the minimization procedure of max.loc. WFs
andrea
--
Andrea Ferretti
National Research Center S3, CNR-INFM ( http://s3.infm.it )
Dip. Fisica, Univ. di Modena e Reggio E. (Italy)
Tel: +39 059 2055301; Fax: +39 059 374794; Skype: andrea_ferretti
URL: http://www.nanoscience.unimo.it
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