[Pw_forum] the high symmetry line of BCT phonon dispersion band structures
Ari P Seitsonen
Ari.P.Seitsonen at iki.fi
Mon Dec 15 23:20:24 CET 2014
Dear S. Appalakondaiah,
As a matter of fact the cells are not very different: If you exchange
the two vectors and take the inverse of the third one you will get the
other case. Figuring out the corresponding directions is a rewarding and
useful exercise - you might also learn something about the symmetry
operations, three-dimensional lattices etc while doing it. Good Luck! :)
Greetings from Paris,
apsi
-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
Ari Paavo Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
Ecole Normale Supérieure (ENS), Département de Chimie, Paris
Mobile (F) : +33 789 37 24 25 (CH) : +41 79 71 90 935
On Tue, 16 Dec 2014, Kondaiah Samudrala wrote:
>
> Dear Sir,
>
> I Completed the Phonon calculations with IBRAV=7 option...Its quite difficult to reperform the calculations. Can you please provide the IBZ path or source for obtain the IBZ???
>
> with regards
>
> S. Appalakondaiah
>
> PhD student
>
> University of Hyderabad
>
>
> On Tue, Dec 16, 2014 at 1:22 AM, Kondaiah Samudrala <konda.physics at gmail.com> wrote:
> Dear all,
> I am still confused with notation of Ibrav=7 in pwscf. The IBRV=7 primitive cell vectors in pwscf are quite different from any other. See below for two cases of primitive vectors IBRAV=7
> Case1
> For. e.g. In pwscf primitive vectors of IBRV=7 are
> crystal axes: (cart. coord. in units of a)
> a(1) = ( 0.500000 -0.500000 c/a)
> a(2) = ( 0.500000 0.500000 c/a )
> a(3) = ( -0.500000 -0.500000 c/a )
> Case 2
> On the other hand, generally people used as (from published papers)
> crystal axes: (cart. coord. in units of a)
> a(1) = ( -0.500000 0.500000 c/a)
> a(2) = ( 0.500000 -0.500000 c/a )
> a(3) = ( 0.500000 0.500000 -c/a ) .
>
> This variation leads to changes in reciprocal vectors and then IBZ path. >From Wikipedia (http://www.sciencedirect.com/science/article/pii/S0927025610002697) and http://www.cryst.ehu.es/ , I obtained the IBZ path for
> case 2. But, what about the IBZ path of case 1 primitive cell vectors?? Is both are same ??? But Xcrysden showing something else than regular Gamma, Z, Sigma, P and N points .
>
> I feel puzzled, would some one give some idea about this? any help will be appreciated
> with regards
> S. Appalakondaiah
> PhD StudentUniversity of Hyderabad
>
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