[Wien] Raman cross section

[Torsten Weissbach]

Hello,

for some time I have tried to calculate the Raman tensor for GaAs using
the second derviative of the force with respect to the electrical field
with WIEN. The field was applied as sawtooth potential (the default
choice) over two supercells with c parallel to the 100 and 110 fcc
directions. The symmetry was lowered  by removing all symmetry
operations from the .struct and adding all L,M values for the lattice
harmonics in .in2. However, it seems impossible to produce any
non-linear behaviour of the forces, which should occur at least in case
of the 110 field. Additionally, the Born effective charge, which can be
calculated from the slope, is also not in accordance with the known
value. Now I'm puzzled whether there are still other options which
should be altered or I made mistakes, and if it is principally possible
to use the efield in lapw0 for this purpose.
Thanks for your help,
Torsten