On Mar 5, 2010, at 2:53 PM, Elie Moujaes wrote:
> Dear all,
>
> I read that if we are trying to calculate the band structure, it is better to
> use {tpiba_b} in ATOMIC POSITIONS rather than {crystal}. Is the only
> difference related to the points that will be plotted at the end because one
> is wrt to cartesian and the other relative to crystallographic axes?
>
>
I never used tpiba_b or crystal_b. Nevertheless, by reading the
Doc/INPUT_PW.txt I understand that it is not a matter of tpiba vs crystal, but
of tpiba_b/crystal_b vs tpiba/crystal. Using either tpiba or crystal, you must
specify the full list of k-points you want to show in your band structure plot.
On the contrary, the *_b options (tpiba_b/crystal_b) allow to specify, for each
given line in the Brillouin zone, only the 1st and last point, together with
the number of points along that line.
As an example, you can replace
K_POINTS {crystal}
5
0.0 0.0 0.0 1.0
0.1 0.0 0.0 1.0
0.2 0.0 0.0 1.0
0.3 0.0 0.0 1.0
0.4 0.0 0.0 1.0
0.5 0.0 0.0 1.0
with
K_POINTS {crystal_b}
2
0.0 0.0 0.0 5.0
0.5 0.0 0.0 5.0
The choice of either crystal_b or tpiba_b is instead driven by in which
coordinate system (crystallographic axes or cartesian, respectively) you find
easier to write the
components of the k-points you need.
Giovanni
--
Giovanni Cantele, PhD
CNR-SPIN and Dipartimento di Scienze Fisiche
Universita' di Napoli "Federico II"
Complesso Universitario M. S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
Phone: +39 081 676910 - Fax: +39 081 676346
Skype contact: giocan74
ResearcherID: http://www.researcherid.com/rid/A-1951-2009
Web page: http://people.na.infn.it/~cantele
http://www.nanomat.unina.it
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