[QE-users] ph.x Raman calculations

[Lorenzo Paulatto]

Hello you can take into account anharmonicity with the d3q code which is included in QE, but also has its own homepage at https://anharmonic.github.io/ where you may find more documentation and examples. In particular, I recently added an example on how to compute the vibrational spectral weight measured by Raman, i.e. like in fig.3 of PhysRevLett.125.145301. It is in the MgO example.

There is currently no automatic way to include both Raman cross section and anharmonic phonon line shape in the same calculation, but this can be easily done by hand.
hth
--
Lorenzo Paulatto - Paris
On Mar 29 2021, at 6:53 pm, Jessica Johnson <jj611 at soe.rutgers.edu> wrote:
>
> Hello QE world,
>
>
> I have a very general question about Raman calculations (I will include that I am using QE version 6.4.1 per the posting guidelines in case that helps my answer my question).
>
> Background: I am calculating Raman shifts in strained 2D MoS2 polymorphs.
>
> It was mentioned to me to by a non-QE user (but a computational chemist) that adding a correction for anharmonicity is sometimes done for Raman calculations, at least in other software packages. Having read "QUANTUM ESPRESSO: a modular and open-source software project for quantum simulations of materials", I understood that anharmonicity is taken into account with the inclusion of second and third order energy derivatives. Am I understanding this correctly? If I am, I would conclude that the suggestion made to me (referenced above) would be moot.
>
> If I am misunderstanding, are there post-processing procedures I should include?
>
> (This is my first time posting. I believe I have adhered sufficiently to the posting guidelines, but apologies in advance if I missed something.)
>
> thank you,
> Jessica Johnson
> Graduate Research Assistant
> Materials Science and Engineering Department
> Rutgers University, New Brunswick
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