# Quantum ESPRESSO (pw) & phono3py calculation¶

Quantum espresso package itself has a set of the force constants calculation environment based on DFPT. But the document here explains how to calculate phonon-phonon interaction and related properties using phono3py, i.e., using the finite displacement and supercell approach.

An example for QE (pw) is found in the example-phono3py/Si-QE directory.

To invoke the QE (pw) interface, --qe option has to be always specified:

% phono3py --qe [options] [arguments]


When the file name of the unit cell is different from the default one (see Default unit cell file name), -c option is used to specify the file name. QE (pw) unit cell file parser used in phono3py is the same as that in phonopy. It can read only limited number of keywords that are shown in the phonopy web site (http://phonopy.github.io/phonopy/qe.html#qe-interface).

## Workflow¶

1. Create supercells with displacements

% phono3py --qe -d --dim="2 2 2" -c Si.in


In this example, probably 111 different supercells with displacements are created. Supercell files (supercell-xxx.in) are created but they contain only the crystal structures. Calculation setting has to be added before running the calculation.

2. Run QE (pw) for supercell force calculations

Let’s assume that the calculations have been made in disp-xxx directories with the file names of Si-supercell.in. Then after finishing those calculations, Si-supercell.out may be created in each directory.

3. Collect forces

FORCES_FC3 is obtained with --cf3 options collecting the forces on atoms in QE (pw) calculation results:

% phono3py --qe --cf3 disp-00001/Si-supercell.out disp-00002/Si-supercell.out ...


or in recent bash or zsh:

% phono3py --qe --cf3 disp-{00001..00111}/Si-supercell.out


disp_fc3.yaml is used to create FORCES_FC3, therefore it must exist in current directory.

1. Calculate 3rd and 2nd order force constants

fc3.hdf5 and fc2.hdf5 files are created by:

% phono3py --qe --dim="2 2 2" -c Si.in --sym-fc

2. Calculate lattice thermal conductivity, e.g., by:

% phono3py --qe --dim="2 2 2" -c Si.in --pa="0 1/2 1/2 1/2 0 1/2 1/2 1/2 0" \
--mesh="11 11 11" --fc3 --fc2 --br