[QE-users] IR calculation for oriented single crystal

[John Kendrick]

Hi Zac,

You might look at a Python package called PDielec on GitHub ( 
https://github.com/JohnKendrick/PDielec ).  It has the capability of 
calculating the IR spectrum (reflectance, absorption and transmission) 
for single crystals either as thick slabs or thin films.  For powders it 
uses an effective medium theory approach to calculating the frequency 
dependent permittivity, from which the spectrum can be determined.  It 
can also be used to view the phonon mode molecular and atomistic motion 
and provides some basic break-down of the energy in each mode in terms 
of internal and external modes.

It has an interface to several packages, including Quantum Espresso, 
VASP, CRYSTAL, AbInit and CASTEP.

John


Subject:
[QE-users] IR calculation for oriented single crystal
From:
Zack Gainsforth <zackg at berkeley.edu>
Date:
18/03/2022, 05:23

To:
Quantum ESPRESSO users Forum <users at lists.quantum-espresso.org>


Hi All,

I have set up a calculation using pw.x -> ph.x -> dynmat.x successfully and plotted myself an IR spectrum.  The match to the experimental spectrum is good.  However, this is an IR spectrum assuming a powder where the photons are exciting all the modes.  I’d now like to calculate the spectrum for a single crystal and specify the electric vector of the photon relative to the crystal.  It should preferentially excite certain modes.

Is there a straightforward way to do this using ph.x + dynmat.x?  Or perhaps a way to read/print the dipole vectors for each mode so I can dot it with my photon’s e-field?  Or another way of thinking about this which is more efficient?  (Maybe I missed something in the documentation!)

Thanks,

Zack

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