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

Kondaiah Samudrala konda.physics at gmail.com
Mon Dec 15 23:35:14 CET 2014

```Dear Prof. Ari Paavo Seitsonen

Thank you very much.. I will look on that

with regards
S. Appalakondaiah
PhD Student

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/
> <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 Student