Phonopy manual¶
What is phonopy?¶
Phonopy is an open source crystal phonon analyzer implemented in Python. VASP and Wien2k interfaces are built-in, however in principle any code that can calculate forces on atoms can be used together. The selected features are as follows:
- Phonon dispersion relation (band structure)
- Phonon DOS and partial-DOS
- Phonon thermal properties, free energy, heat capacity, and entropy
- Thermal expansion within quasi-harmonic approximation
Phonopy is based on a real-space supercell approach. Phonopy calculates phonon frequencies from force constants with respect to real space displacements in a supercell. The force constants can be calculated from atomic forces when an atom is slightly displaced in a supercell (Parlinsk-Li-Kawasoe method).
Since the force-constants interface is also prepared, if you already have force constants in real space, e.g., using DFPT in VASP (interface for VASP), you don’t need to calculate atomic forces.
In practice, phonopy provides automated pre- and post-processes to calculate the phonon properties. Since crystal symmetry is fully and automatically included, force calculation can be minimized. In the pre-process, you can obtain supercells including displacements from your crystal structure. You can calculate atomic-forces using the supercells by your favorite calculator (e.g., VASP or WIEN2k). In the post-process, the atomic forces are collected and the phonon properties are calculated.
Index¶
License¶
GPL v2
Contact¶
If you have any questions, bug reports, and comments, please contact me.
- Author: Atsushi Togo
- e-mail: atz.togo@gmail.com