[Pw_forum] phonon dispersion calculations
Eyvaz Isaev
eyvaz_isaev at yahoo.com
Tue Aug 8 16:02:49 CEST 2006
Hi,
You can generate these q-points for yourself.
The number of q-points depends on how the phonon
spectrum is complex (how many intersections, softening
of phonon branches). 20 for each high symmetry
direction looks reasonable.
Just have a look Bradley-Cracknell textbook about BZ
vertices and then divide each direction as much as you
like (see above). Do not forget that you have to
transform these q-points to cartesian.
Bests,
Eyvaz.
--- Tuhina Kelkar <tr.kelkar at ncl.res.in> wrote:
> Hi! I am a new user of QEspresso. I want to use it
> to calculate the phonon dispersion for MgH2 along
> the following high symmetry points: Gamma to X to M
> to Gamma to Z to R to A to Z.
> But I am not being able to construct the matdyn.in
> file. How does one decide on the number of q-points?
> And how to go about creating this list of q-points
> to be used in matdyn.in?
> I have already obtained the IFC's and the following
> is the resulting q2r.out file:
> reading grid info from file dyn0
> reading force constants from file dyn1
> Dielectric Tensor not found
> nqs= 1
> q= 0.00000000 0.00000000 0.00000000
> reading force constants from file dyn2
> nqs= 1
> q= 0.00000000 0.00000000 -0.74850299
> reading force constants from file dyn3
> nqs= 2
> q= 0.00000000 -0.50000000 0.00000000
> q= 0.50000000 0.00000000 0.00000000
> reading force constants from file dyn4
> nqs= 2
> q= 0.00000000 -0.50000000 -0.74850299
> q= 0.50000000 0.00000000 -0.74850299
> reading force constants from file dyn5
> nqs= 1
> q= -0.50000000 -0.50000000 0.00000000
> reading force constants from file dyn6
> nqs= 1
> q= -0.50000000 -0.50000000 -0.74850299
> q-space grid ok, #points = 8
> fft-check success (sum of imaginary terms <
> 10^-12)
> Thanks in advance.
> Tuhina
>
__________________________________________________
Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around
http://mail.yahoo.com
More information about the Pw_forum
mailing list