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**Questions and Answers / Re: Raman Spectra**

« **on:**July 16, 2021, 16:48 »

Hello,

Just to follow up my query - beyond QuantumATK I have recently tried using GPAW code integrated with ASE (https://wiki.fysik.dtu.dk/gpaw/tutorials/elphraman/elphraman.html?fbclid=IwAR1a-qGnbwyGFcEmi0oegE5OfPold1ndlpzzHcy2PXLx2vrbj3ixfIuyELU) where from the documentation it follows how the momentum matrix elements for Raman spectra are computed and called.

Even though the implementations of Raman spectra in both codes are different (as far as I know in QuantumATK momentum matrix elements are used to find susceptibility tensor from the Kubo-Greenwood formula, while GPAW uses these to compute Raman tensor directly as follows from third-order Fermi's golden rule) - I am still wondering how to call the momentum matrix elements in QuantumATK and how these are implemented.

I have found out how to call the susceptibility derivatives when computing Raman spectra, but I am totally clueless about how susceptibility tensor calls momentum matrix elements when it is evaluated by OpticalSpectrum object: https://docs.quantumatk.com/manual/Types/OpticalSpectrum/OpticalSpectrum.html

Would it be possible to ask for some hint?

Thanks for any potential help!

Just to follow up my query - beyond QuantumATK I have recently tried using GPAW code integrated with ASE (https://wiki.fysik.dtu.dk/gpaw/tutorials/elphraman/elphraman.html?fbclid=IwAR1a-qGnbwyGFcEmi0oegE5OfPold1ndlpzzHcy2PXLx2vrbj3ixfIuyELU) where from the documentation it follows how the momentum matrix elements for Raman spectra are computed and called.

Even though the implementations of Raman spectra in both codes are different (as far as I know in QuantumATK momentum matrix elements are used to find susceptibility tensor from the Kubo-Greenwood formula, while GPAW uses these to compute Raman tensor directly as follows from third-order Fermi's golden rule) - I am still wondering how to call the momentum matrix elements in QuantumATK and how these are implemented.

I have found out how to call the susceptibility derivatives when computing Raman spectra, but I am totally clueless about how susceptibility tensor calls momentum matrix elements when it is evaluated by OpticalSpectrum object: https://docs.quantumatk.com/manual/Types/OpticalSpectrum/OpticalSpectrum.html

Would it be possible to ask for some hint?

Thanks for any potential help!