Dear QE users and developers,
I have some questions about phonon calculations:
1): what is the unit of the displacement vector in *dyn* files? I think the
displacement vector is under the "1 1" as shown below.
######################################################################
Dynamical Matrix in cartesian axes
q = ( 0.000000000 -1.000000000 0.000000000 )
1 1
0.24766291 0.00000000 -0.00000000 0.00000000 0.00000000
0.00000000
0.00000000 0.00000000 0.35585327 0.00000000 0.00000000
0.00000000
0.00000000 0.00000000 0.00000000 0.00000000 0.24766291
0.00000000
######################################################################
2): in the output file matdyn.modes as shown below. There are also some
vectors that are similar with the displacement vector in *dyn* files. The
vector is under the "freq ( 1) = -0.000000 [THz] = -0.000000 [cm-1]". But
obviously, the vectors in file matdyn.modes and *dyn* files are different. What
is the difference between two vectors. And what is the unit of the vector in
matdyn.modes?
######################################################################
diagonalizing the dynamical matrix ...
q = 0.0000 0.0000 0.0000
**************************************************************************
freq ( 1) = -0.000000 [THz] = -0.000000 [cm-1]
( 0.649741 0.000000 0.275541 -0.000000 0.043740 -0.000000 )
( 0.649741 0.000000 0.275541 -0.000000 0.043740 -0.000000 )
freq ( 2) = 0.000000 [THz] = 0.000010 [cm-1]
( 0.146859 0.000000 -0.243532 0.000000 -0.647399 0.000000 )
( 0.146859 0.000000 -0.243532 0.000000 -0.647399 0.000000 )
#######################################################################
3) When I use phonopy to calculate phonon dos. When I choose the same q denser
in QE and Phonopy. But the output q is different. Do you know the reasons?
For example: In fcc Silicon, when the q density is set 2*2*2 in two software.
The output Q is shown as below.
#############
QE: Q POINTS
q = 0.0000 0.0000 0.0000
q = 0.5000 -0.5000 0.5000
q = 0.0000 -1.0000 0.0000
phonopy:
- q-position: [ 0.2500000, 0.2500000, 0.2500000 ]
- q-position: [ -0.2500000, 0.2500000, 0.2500000 ]
#############
4)And what is the difference between phonopy and QE dfpt(Except the difference
between finite displacement and dfpt)
Maybe I have so many questions. But I hope someone can help me!
Thanks so much in advance!
Best regards,
Zeli
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