[Pw_forum] propagation direction in the input file

Li YL ylli at theory.issp.ac.cn
Fri Apr 17 10:37:37 CEST 2009

```Dear Eyvaz,

>This one can be done using matdyn.x, too.
Can you give me example file to finish  LO-TO spliting using matdyn.x? I noticed that for insulator,  by default, ph.x firstly calculate electric field and effective charges. Why?

>  If the difference in between number of atoms not too much, I would prefer hexagonal.
There are much difference in between nubmers of atoms. There are 30 atoms in unit cell. But in its primitive cell,
the number of atoms is only 10.

By the way, now I can obtain dielectriic constants (high frequency dielectric constants) and effective charges, but I don't know how to get static dielectrin constant and polar charges? can you give me some suggestions? Thanks a lot.

Best regards,

Yanling Li,

Institute of solid states physics, CAS, China.

-------------------------------------------------------------------------

>>Dear Li,

>>This one can be done using matdyn.x, too.

>>My system has hexagonal symmetry and its primitive cell is rhombohedral.

>>If the difference in between number of atoms not too much, I would prefer hexagonal, as it has higher symmetry >>and this will make things easier.

>>From  matdyn.f90:
>
> !  Then, if (.not.dos) :
> !     nq         number of q-points
>  !     (q(i,n), i=1,3)    nq q-points in 2pi/a units
>  !  If q = 0, the direction qhat (q=>0) for the non-analytic part
>  !  is extracted from the sequence of q-points as follows:
>  !     qhat = q(n) - q(n-1)  or   qhat = q(n) - q(n+1)
>  !  depending on which one is available and nonzero.
>  !  For low-symmetry crystals, specify twice q = 0 in the list
>  !  if you want to have q = 0 results for two different directions
>  !
> Anyway, you should  specify 2 directions like

> x(1) y(1) z(1)
> ........
> x(N-1) y(N) z(N)
>0    0   0  !!!!! Gamma point x(N)=0 y(N)=0 z(N)=0
>x(N+1) y(N+1) z(N+1)
> .........
> x(M) y(M) z(M)

> For a hexagonal lattice  you could try A (00z) --> G(000) --> K(-1/3,2/3,0), as example.

> Hope this helps.

> Bests, Eyvaz.

>--- On Thu, 4/16/09, Li YL <ylli at theory.issp.ac.cn> wrote:

> Dear all users,
>
> Now I've a question on the polar materials. In order to
> get LO-TO splitting, you know, we need to use dynmat.x. In
> the input file for dynmat.x, we need input q(1), q(2), and
> q(3), that is, the propagation direction. I don't know
> how to choose this direction. My system has hexagonal
> symmetry and its primitive cell is rhombohedral.
> Any suggestions are welcome. Thanks in advance.
>
> Bests,
>
> Yanling Li,
>
> Institute of Solid states physics, CAS, P. R. China.

Re: [Pw_forum] propagation direction in the input file

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