[Pw_forum] phonon eigenvectors
Eric Abel
etabel at hotmail.com
Thu Aug 31 06:07:51 CEST 2006
Hello PWSCF users,
I have a question which is sort of a follow-up to a similar question which I
asked previously. Anyway, I was wondering about the imaginary part of the
phonon eigenvectors, which at the time, Stefano had informed me are more or
less arbitrary. At the time that made sense. But now I am trying to make
sense of the following eigenvectors:
q = 0.0000 0.0563 0.0000
**************************************************************************
omega( 1) = -0.308036 [THz] = -10.275037 [cm-1]
( 0.000000 0.000000 0.000000 -0.142674 -0.338669 0.000000 )
( 0.000000 0.000000 0.031918 -0.201463 -0.388896 -0.061613 )
( 0.000000 0.000000 0.019612 -0.123787 -0.367551 -0.058231 )
( 0.000000 0.000000 0.000000 -0.226888 -0.354765 0.000000 )
( 0.000000 0.000000 0.036445 -0.230039 -0.328252 -0.052005 )
( 0.000000 0.000000 0.000000 -0.096682 -0.403396 0.000000 )
omega( 2) = 0.617574 [THz] = 20.600196 [cm-1]
( -0.403925 -0.012145 0.000000 0.000000 0.000000 0.000000 )
( -0.397050 -0.075201 0.000000 0.000000 0.000000 0.000000 )
( -0.397199 -0.075229 0.000000 0.000000 0.000000 0.000000 )
( -0.404073 -0.012149 0.000000 0.000000 0.000000 0.000000 )
( -0.408949 -0.077455 0.000000 0.000000 0.000000 0.000000 )
( -0.416112 -0.012511 0.000000 0.000000 0.000000 0.000000 )
omega( 3) = 0.788199 [THz] = 26.291668 [cm-1]
( 0.000000 0.000000 0.000000 0.389819 -0.233273 0.000000 )
( 0.000000 0.000000 -0.055122 0.347926 -0.110454 -0.017499 )
( 0.000000 0.000000 -0.061881 0.390589 -0.148121 -0.023467 )
( 0.000000 0.000000 0.000000 0.342277 -0.187111 0.000000 )
( 0.000000 0.000000 -0.050913 0.321357 -0.249835 -0.039581 )
( 0.000000 0.000000 0.000000 0.384275 -0.092029 0.000000 )
These are the first 3 (accoustic) modes of the spectrum. If the imaginary
part doesn't matter, then it would appear that the accoustic displacement
along the b-direction is practically zero. However, the imaginary part is
the same magnitude as the displacements in the other orthogonal directions.
Is there any physical meaning to this, or is it just an artifact of the
calculation?
Eric,
Ph.D. Student, M.I.T.
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