Help to calculate the absorption spectrum

Matt W MattWa... at
Thu Jul 10 05:42:04 UTC 2014

Hi Mohamed,

you mentioned in a previous post calculating reflectivity, so I guess you 
need to calculate the whole spectrum?

Unfortunately, the TDDFPT/linear response code currently doesn't have 
intensities, just transition energies. If you want something like the full 
spectrum there are two possibilities I can see:

(i) there is a DFT/PRINT/OPTICAL_CONDUCTIVITY keyword that would give you 
the imaginary part of the dielectric constant in an independent particle 
approximation - BUT, it is not working at the moment. I'm fixing it and 
will hopefully add changes in a few days. This is the easiest approach, but 
is rather crude.
(ii) real time propagation time dependent DFT would give you the spectrum 
from the power spectrum of dipole moment changes in time. Using this 
approach is somewhat trickier than just running ground state calculations, 



On Thursday, July 10, 2014 4:25:40 AM UTC+1, mohamed khuili wrote:
> is what I suggested in question is not feasible with CP2K?
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