def get_default_physical_units(interface_mode=None):
    """Return physical units used for calculators

    Physical units: energy,  distance,  atomic mass, force
    vasp          : eV,      Angstrom,  AMU,         eV/Angstrom
    wien2k        : Ry,      au(=borh), AMU,         mRy/au
    abinit        : hartree, au,        AMU,         eV/Angstrom
    elk           : hartree, au,        AMU,         hartree/au
    qe            : Ry,      au,        AMU,         Ry/au
    siesta        : eV,      au,        AMU,         eV/Angstroem
    CRYSTAL       : eV,      Angstrom,  AMU,         eV/Angstroem
    DFTB+         : hartree, au,        AMU          hartree/au
    TURBOMOLE     : hartree, au,        AMU,         hartree/au

    """

    from phonopy.units import (Wien2kToTHz, AbinitToTHz, PwscfToTHz, ElkToTHz,
                               SiestaToTHz, VaspToTHz, CP2KToTHz, CrystalToTHz,
                               DftbpToTHz, TurbomoleToTHz, Hartree, Bohr)

    units = {'factor': None,
             'nac_factor': None,
             'distance_to_A': None,
             'force_constants_unit': None,
             'length_unit': None}

    if interface_mode is None or interface_mode == 'vasp':
        units['factor'] = VaspToTHz
        units['nac_factor'] = Hartree * Bohr
        units['distance_to_A'] = 1.0
        units['force_constants_unit'] = 'eV/Angstrom^2'
        units['length_unit'] = 'Angstrom'
    elif interface_mode == 'abinit':
        units['factor'] = AbinitToTHz
        units['nac_factor'] = Hartree / Bohr
        units['distance_to_A'] = Bohr
        units['force_constants_unit'] = 'eV/Angstrom.au'
        units['length_unit'] = 'au'
    elif interface_mode == 'qe':
        units['factor'] = PwscfToTHz
        units['nac_factor'] = 2.0
        units['distance_to_A'] = Bohr
        units['force_constants_unit'] = 'Ry/au^2'
        units['length_unit'] = 'au'
    elif interface_mode == 'wien2k':
        units['factor'] = Wien2kToTHz
        units['nac_factor'] = 2000.0
        units['distance_to_A'] = Bohr
        units['force_constants_unit'] = 'mRy/au^2'
        units['length_unit'] = 'au'
    elif interface_mode == 'elk':
        units['factor'] = ElkToTHz
        units['nac_factor'] = 1.0
        units['distance_to_A'] = Bohr
        units['force_constants_unit'] = 'hartree/au^2'
        units['length_unit'] = 'au'
    elif interface_mode == 'siesta':
        units['factor'] = SiestaToTHz
        units['nac_factor'] = Hartree / Bohr
        units['distance_to_A'] = Bohr
        units['force_constants_unit'] = 'eV/Angstrom.au'
        units['length_unit'] = 'au'
    elif interface_mode == 'cp2k':
        units['factor'] = CP2KToTHz
        units['nac_factor'] = Hartree / Bohr  # in a.u.
        units['distance_to_A'] = Bohr
        units['force_constants_unit'] = 'hartree/au^2'
        units['length_unit'] = 'Angstrom'
    elif interface_mode == 'crystal':
        units['factor'] = CrystalToTHz
        units['nac_factor'] = Hartree * Bohr
        units['distance_to_A'] = 1.0
        units['force_constants_unit'] = 'eV/Angstrom^2'
        units['length_unit'] = 'Angstrom'
    elif interface_mode == 'dftbp':
        units['factor'] = DftbpToTHz
        units['nac_factor'] = Hartree * Bohr
        units['distance_to_A'] = Bohr
        units['force_constants_unit'] = 'hartree/au^2'
        units['length_unit'] = 'au'
    elif interface_mode == 'turbomole':
        units['factor'] = TurbomoleToTHz
        units['nac_factor'] = 1.0
        units['distance_to_A'] = Bohr
        units['force_constants_unit'] = 'hartree/au^2'
        units['length_unit'] = 'au'

    return units
Return physical units used for calculators

    Physical units: energy,  distance,  atomic mass, force
    vasp          : eV,      Angstrom,  AMU,         eV/Angstrom
    wien2k        : Ry,      au(=borh), AMU,         mRy/au
    abinit        : hartree, au,        AMU,         eV/Angstrom
    elk           : hartree, au,        AMU,         hartree/au
    qe            : Ry,      au,        AMU,         Ry/au
    siesta        : eV,      au,        AMU,         eV/Angstroem
    CRYSTAL       : eV,      Angstrom,  AMU,         eV/Angstroem
    DFTB+         : hartree, au,        AMU          hartree/au
    TURBOMOLE     : hartree, au,        AMU,         hartree/au