Dear QE users and developers
I run a phonon calculation in SnSe (Roch-salt structure) and I get the
frequencies in the Gamma point (dyn1 file):
q = ( 0.000000000 0.000000000 0.000000000 )
**************************************************************************
freq ( 1) = -0.947936 [THz] = -31.619734 [cm-1]
( 0.463998 0.000000 -0.152295 0.000000 -0.248340 0.000000 )
( -0.708498 0.000000 0.232546 0.000000 0.379201 0.000000 )
freq ( 2) = -0.947936 [THz] = -31.619734 [cm-1]
( -0.267553 0.000000 -0.407542 0.000000 -0.249970 0.000000 )
( 0.408539 0.000000 0.622293 0.000000 0.381690 0.000000 )
freq ( 3) = -0.947936 [THz] = -31.619734 [cm-1]
( 0.115246 0.000000 -0.332981 0.000000 0.419526 0.000000 )
( -0.175974 0.000000 0.508442 0.000000 -0.640593 0.000000 )
freq ( 4) = -0.098311 [THz] = -3.279313 [cm-1]
( -0.486385 0.000000 0.205881 0.000000 0.478423 0.000000 )
( -0.478812 0.000000 0.202675 0.000000 0.470973 0.000000 )
freq ( 5) = -0.098311 [THz] = -3.279313 [cm-1]
( 0.492088 0.000000 0.396133 0.000000 0.329809 0.000000 )
( 0.484426 0.000000 0.389965 0.000000 0.324673 0.000000 )
freq ( 6) = -0.098311 [THz] = -3.279313 [cm-1]
( 0.170660 0.000000 -0.555462 0.000000 0.412533 0.000000 )
( 0.168003 0.000000 -0.546813 0.000000 0.406109 0.000000 )
**************************************************************************
After I use q2r.x and plotphonon to plot the spectrum (using matdyn.x with
asr='crystal') I get the frequencies in the Gamma point: 0,0,0 (for
acoustic, which is good) and ~ -1 -1 3 THz for the optics ,which is
strange. From where the 3 THz frequency come from? Which frequencies are
more reliable, the original ones or those of matdyn?
I note that it is probably unstable structure but I still want to now what
are the unstable modes.
Thank you very much
Uri Argaman
Ben-Gurion University
Israel
_______________________________________________
Pw_forum mailing list
[email protected]
http://pwscf.org/mailman/listinfo/pw_forum
