`phonopy-vibspec`

Purpose

Simulate IR and Raman spectra. This requires the phonon eigenvalues and eigenvectors, wich are readily obtained from Phonopy. Then, calculation(s) of the dielectric matrix provide the IR and Raman intensities (see 10.1039/C7CP01680H).

Note: this is actually a simpler (and packaged!) version of Phonopy-Spectroscopy. The main difference with the latter is that this package does not include phonon line widths (and thus does not require phono3py). If you are interested in that (or polarized Raman), use their code instead :)

Install

To install this package, you need a running Python 3 installation (Python >= 3.10 recommended), and

pip3 install git+https://github.com/pierre-24/phonopy-vibspec.git

Note: as this script install programs, you might need to add their location (such as $HOME/.local/bin, if you use --user) to your $PATH, if any.

Usage

Common procedure:

# 1. Create POSCAR of supercell:
# (from https://phonopy.github.io/phonopy/vasp-dfpt.html#vasp-dfpt-interface)
phonopy -d --dim="1 1 1" -c unitcell.vasp 
# Note: use preferentially a larger cell

# 2. cleanup
rm POSCAR-*
mv SPOSCAR POSCAR

# 3. Run VASP using `IBRION=8` or `IBRION=6` with appropriate `POTIM`

# 4. Extract force constants (a `force_constants.hdf5` file is created)
phonopy --hdf5 --fc vasprun.xml

Create files to vizualize the modes in VESTA:

phonpy-vs-modes --modes="4 5 6"

For infrared:

# 1. Run a calculation with `LEPSILON = .TRUE.` **on the unit cell**

# 2. Extract Born effective charges from calculations
phonopy-vasp-born vasprun.xml > BORN

# 3. Get IR spectrum
phonopy-vs-ir spectrum.csv

For Raman:

# 1. Get displaced geometries
phonopy-vs-prepare-raman

# 2. Create folders for calculations
for i in dielec-*.vasp; do a=$(i%.vasp); mkdir -p $a; cd $a; ln -s ../$i POSCAR; cd ..; done; 

# 3. Run calculations with `LEPSILON = .TRUE.` for each displaced geometry

# 4. Collect dielectric constants
phonopy-vs-gather-raman dielec-*/vasprun.xml

# 4. Get Raman spectrum
phonopy-vs-raman spectrum.csv

Who?

My name is Pierre Beaujean, and I have a Ph.D. in quantum chemistry from the University of Namur (Belgium). I'm the main (and only) developer of this project, used in our lab. I use this in the frame of my post-doctoral research in order to study batteries and solid electrolyte interphrase, and I developed this project to ease my life.

Note: due to my (quantum) chemistry background, we may speak of similar things using a different vocabulary.