[gpaw-users] Polarizability Tensor

[Frank von Horsten]

Dear all,

I would like to calculate Raman scattering activities with GPAW. For that I
need the polarizability tensor.

I saw that there is a get_polarizability() function in the
DielectricFunction class. However, I am relatively new to GPAW and just
about to familiarize myself with the program. Hence, I'm not sure how to
use it correctly.

Can anyone give me some insight how to calculate the elements of the
polarizability tensor?

To be more specific, let's say we start with an ASE atoms object "atoms"
and have defined a GPAW calculator "calc":
0.) atoms.set_calculator(calc)
1.) atoms.get_potential_energy()
2.) calc.diagonalize_full_hamiltonian(nbands=X)
3.) calc.write("system.gpw",all)
4.) df=DielectricFunction('system.gpw',hilbert=not True, eta=0.1, ecut=10,
frequencies=omega)
5.) a0,a=df.get_polarizability(filename=None,direction='x')

Would that be the way to calculate the matrix element \alpha_xx at
frequency omega?
If so, I would understand that by changing the direction='y' or 'z' I would
get \alpha_yy and \alpha_zz. However, I don't know how to obtain the off
diagonal elements xy etc.
So I reckon that there is something fundamental, which I misunderstood so
far.

Any hints would be greatly appreciated! I also saw that there is a new
ResonantRaman class within ASE. Does anyone know if the is already usable
or still work in progress?

Thanks and best wishes,

Frank
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