[Pw_forum] the high symmetry line of BCT phonon dispersion band structures

[Ari P Seitsonen]

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
>