Introduction¶
Following files are required in your working directory.
- INPHON, POSCAR, and FORCES or FORCE_CONSTANTS are essential whenever running phonopy.
- DISP may be required to create FORCES.
In the case of frozen phonon approach, there are three steps.
- Create supercells and introduce atomic displacements. Each supercell contains one atomic displacement. This can be done using LSUPER = .TRUE. tag in INPHON. See Examples of INPHON. After running phonopy, the files of supercells with atomic displacements like as POSCAR-001, POSCAR-002, ..., are created in current directory (the file format and names are different in WIEN2k mode.) The files DISP and SPOSCAR are also created. The file SPOSCAR is the perfect supercell that contains no atomic displacement. This file is not usually used.
- Calculate forces on atoms of the supercells with atomic displacements. Currently phonopy prepares VASP and WIEN2k interfaces to semi-automatically create FORCES. After obtaining forces on atoms that calculated by some means (it’s out of phonopy), they are summarized in FORCES file.
- Calculate phonon frequencies. See Analyze phonon structure.
If you already have force constants, the first and second steps can be omitted. Your force constants have to be converted to the format that phonopy can read. See FORCE_CONSTANTS. The VASP interface to convert force constants is prepared.
Analyze phonon structure¶
Once FORCES or FORCE_CONSTANTS is prepared, analyzing phonon, e.g., DOS, PDOS, band structure, or thermal properties, is easy. Phonopy provides several ways to show those results. You can order them via Command options and Setting tags.
- Graph plot on display (Graph plotting (-p))
- Graph plot to PDF file (Save graph plotting to PDF file (-p -s))
- Text data (Output files)