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

Kondaiah Samudrala konda.physics at gmail.com
Mon Dec 15 22:27:37 CET 2014

```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

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