下面以Si为例，DFPT计算声子谱。

This procedure is similar with that in previous article. The difference is in STEP 4.

calculation of phonon frequency at any given list of q-vectors (to get DOS or dispersion)

&input
  asr = 'simple'
  amass(1) = 28.0855
  flfrc = 'si.k444.fc'
  flfrq = 'si.freq'
  q_in_band_form = .true.
  q_in_cryst_coord = .true.
/
5
  0.0000 0.0000 0.0000 30 !Gamma
  -0.500 0.0000 -0.500 10 !X
  0.0000 0.3750 -0.375 20 !K
  0.0000 0.0000 0.0000 30 !Gamma
  0.0000 0.5000 0.0000 1 !L

Also, matdyn.x si.4_matdyn_2_dispersion.in

STEP 5

use plotband.x to obtain the data of si.freq

si.freq
0 550
si.phonon.bands.xmgr
si.phonon.bands.ps
0
50 0