[CP2K-user] [CP2K:19101] No agreement between the LR and RT absorption spectra

[Natalia K]

Dear community,

I am calculating the absorption spectra for a silver chain using both 
linear response (TDDFPT) and real-time propagation implemented in CP2K 9.1. 
Within the RT propagation, I apply a delta kick in all three directions and 
then take the Fourier transform of the dipole moment and get the average 
(over three directions) spectrum that is in a very good agreement with the 
literature. In particular, with another GGA linear-response calculation 
with the Gaussian code (image attached, top - my results, bottom - 
reference). Within the TDDFPT approach, I calculate the oscillator strength 
which should give the same frequencies as the real-time approach, but it 
doesn't. In the figure attached, the oscillator strength is plotted with 
impulses. I tested many different parameters but LR never agrees with RT. I 
also tested a simpler system, a water molecule, and got a better agreement 
between the two methods, but still not as perfect as here, for instance: 
https://nwchemgit.github.io/RT-TDDFT.html#absorption-spectrum-of-water

I would appreciate any help or suggestion. I attach both RT and LR input 
files used to obtain the results on the figure.

Best regards,

Natalia

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