[Pw_forum] phonon calculation with ultrasoft potentials

[Marcel Mohr]

Dear espresso-users,

I am calculating wurtzite CdSe with the PBE Vanderbilt pseudos provided by 
the pwscf page. Lattice constant is very good. I am using a cutoff of 50 
Ry, (that is even far beyond convergence).
When I try to calculate phonon frequencies, I obtain acoustic phonon at 30 
and 90 cm^-1. And the higehst optical phonon is twice as it should be.

This is my ph.x input file
  &inputph
   tr2_ph=1.0d-14,
   prefix='cdse',
   epsil=.true.,
   amass(1)=112.4,
   amass(2)=78.96,
   fildyn='cdse.dynG',
  /
0.0 0.0 0.0

Maybe the electric field has to be included in the calculation, 
but I do not know how.

Best Regards

Marcel Mohr