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

Paolo Giannozzi paolo.giannozzi at uniud.it
Mon Dec 15 22:17:28 CET 2014

```You can set ibrav=0 and choose the lattice vectors you want

Paolo

On Tue, 2014-12-16 at 01:22 +0530, Kondaiah Samudrala 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 Student
>
>
>
>
>
>
>
>
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--
Paolo Giannozzi, Dept. Chemistry&Physics&Environment,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222

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