Interfaces to calculators

The interfaces for VASP, Wien2k, Pwscf, Abinit, Elk and CRYSTAL are built in to the usual phonopy command. See the command options and how to invoke each of them at Choice of force calculator.

Physical unit system for calculator

Physical unit systems used for the calculators are as follows:

        | Distance   Atomic mass   Force         Force constants
VASP    | Angstrom   AMU           eV/Angstrom   eV/Angstrom^2
Wien2k  | au (bohr)  AMU           mRy/au        mRy/au^2
Pwscf   | au (bohr)  AMU           Ry/au         Ry/au^2
Abinit  | au (bohr)  AMU           eV/Angstrom   eV/
Siesta  | au (bohr)  AMU           eV/Angstrom   eV/
elk     | au (bohr)  AMU           hartree/au    hartree/au^2
CRYSTAL | Angstrom   AMU           eV/Angstrom   eV/Angstrom^2

For these sets of physical properties, phonon frequency is calculated in THz.

Default file name, value, and conversion factor

Default unit cell file name for calculator

Without specifying -c option, default file name for unit cell is used as shown below:

Wien2k  | case.struct
Pwscf   |
Abinit  |
Siesta  | input.fdf
Elk     |
CRYSTAL | crystal.o

Default displacement distances

Without specifying DISPLACEMENT_DISTANCE tag or --amplitude option, default displacement distance is used when creating supercells with displacements CREATE_DISPLACEMENTS = .TRUE. or -d option. The default value is dependent on calculator, and the list is shown below:

VASP    | 0.01 Angstrom
Wien2k  | 0.02 au (bohr)
Pwscf   | 0.02 au (bohr)
Abinit  | 0.02 au (bohr)
Siesta  | 0.02 au (bohr)
Elk     | 0.02 au (bohr)
CRYSTAL | 0.01 Angstrom

Default unit conversion factor for non-analytical term correction

VASP    | 14.399652
Wien2k  | 2000
Pwscf   | 2
Abinit  | 51.422090
Siesta  | 51.422090
Elk     | 1
CRYSTAL | 14.399652

Interface to VASP DFPT force constants

Using VASP DFPT feature, force constants are directly calculated. Phonopy VASP DFPT interface reads vasprun.xml and creates FORCE_CONSTANTS file.

Interface to FHI-aims forces

For FHI-aims, there is a special command, phonopy-FHI-aims. This tool is maintained by FHI-aims community and questions may be sent to the FHI-aims mailing list.