[Pw_forum] Help for reading data

[Paolo Giannozzi]

On Tuesday 22 February 2005 19:14, wei luo wrote:

> Now I get the *.dnyG file. But I don't know how to read it and
> identify the Raman vibration mode.

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"make tools" compiles code "dynmat.x" in the pwtools/ directory.
It reads the dynamical matrix file at q=0 and can

- apply the acoustic sum rule, so that you get omega=0 for
  translation modes at q=0
- add the non-analytical terms that are responsible for the TO-LO
  splitting,  calculate IR cross sections (provided that the dynamical
  matrix file contains the effective charges, option "epsil=.true." in ph.x)
- produce a file with eigendisplacements that can be directly plotted
  by "molden"
- Raman cross sections can also be calculated but it is much trickier

It shouldn't be difficult to classify phonon modes in a 8-atom system.
In any case, the bunch of numbers following each frequency are, for 
each atom: Re(u_x) Im(u_x) Re(u_y) Im(u_y) Re(u_z) Im(u_z), where u 
is the normalized eigendisplacement. The imaginary terms are obviously
zero for q=0

Paolo
-- 
Paolo Giannozzi             e-mail:  giannozz at nest.sns.it
Scuola Normale Superiore    Phone:   +39/050-509876, Fax:-563513 
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