Introduction

‘Introduction to phonopy’ slides

A presentation in pdf for introduction to phonopy is downloaded ***here***.

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Features

Band structure

Phonon band structure is calculated for the specified band paths. See Band structure tags.

Density of states

Total and partial density of states are calculated based on the q-point sampling mesh (Phonon density of states (DOS) tags). Smearing parameter is set by SIGMA tag or --sigma option.

Group velocity

Phonon group velocity is calculated from first derivative of dynamical matrix. See Group velocity.

Thermal properties

Helmholtz free energy, heat capacity at constant volume, and entropy at temperatures are calculated from the phonon frequencies on the q-point sampling mesh. See Thermal properties related tags.

Thermal properties at constant pressure and thermal expansion

Gibbs free energy, heat capacity at constant pressure, and thermal expansion are calcualted with quasi-harmonic approximation. See Quasi harmonic approximation.

Measure of how far atoms move at finite temperature

How far atoms are displaced from their equilibrium positions at temperatures is calculated as mean square displacements. See Thermal displacements.

Calculation of mode Grüneisen parameters

A script gruneisen is used for calculating mode Grüneisen parameters in band structure style and mesh sampling style. See the details at Calculation of mode Grüneisen parameters.

Normal mode analysis

Irreducible representations are assigned using polarization vectors of phonon normal modes (Characters of irreducible representations). Atomic displacements corresponding to the real part of the polarization vectors are obtained (Create modulated structure). This may be applied for research of the second-order like structural phase transition.

Animation

Phonon mode is visualized by animation. See Create animation file.

Plot and output

The results of DOS, PDOS, band structure, and thermal properties are immediately plotted by specifying -p option (Graph plotting). When -s option is set together with the -p option, the plot is stored in the PDF file (-p -s). In addition those results are saved in output text files (Output files), too.

Work flow

Work flow of phonopy is shown schematically. There are two ways to calculate, (1) atomic forces from finite displacements and (2) given force constants. You can choose one of them. Forces on atoms or force constants are calculated by your favorite calculator (shown by the diamonds in the work flow). The boxes are jobs being done by phonopy, and the circles are input and intermediate output data structures.

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Work flow of phonon calculation