[Pw_forum] phonon dispersion calculations

[Tuhina Kelkar]

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
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