2. Phonon Dispersion

This is a simple example of how to compute the phonon dispersion using the MatterSim.

2.1. Import the necessary modules

First we import the necessary modules. It is worth noting that we have a built-in workflow for phonon calculations using phonopy in MatterSim.

import numpy as np
from ase.build import bulk
from ase.units import GPa
from ase.visualize import view
from mattersim.forcefield.potential import MatterSimCalculator
from mattersim.applications.phonon import PhononWorkflow

Note

The phonopy package is required to compute the phonon dispersion. You can install it by running the following command:

conda install -c conda-forge phonopy==2.14.0

2.2. Set up the MatterSim calculator

# initialize the structure of silicon
si = bulk("Si")

# attach the calculator to the atoms object
si.calc = MatterSimCalculator()

2.3. Set up the phonon workflow

ph = PhononWorkflow(
    atoms=si,
    find_prim = False,
    work_dir = "/tmp/phonon_si_example",
    amplitude = 0.01,
    supercell_matrix = np.diag([4,4,4]),
)

2.4. Compute the phonon dispersion

has_imag, phonons = ph.run()
print(f"Has imaginary phonon: {has_imag}")
print(f"Phonon frequencies: {phonons}")

2.5. Inspect the phonon dispersion

Once the calculation is done, you can find the phonon plot in the work directory. In this case, you find the plot in the directory /tmp/phonon_si_example, and here is the phonon dispersion plot for the example above.