Keyword-Reference

The cell and param file keywords used specifically for phonon and related calculations are listed here alphabetically with brief descriptions.

CELL file keywords

PHONON_FINE_KPOINT_LIST

List of phonon wavevectors on the fine grid (Block)
Phonon frequencies are calculated on a coarse set of wavevectors using DFPT and interpolated onto this finer list of points.

PHONON_FINE_KPOINT_MP_GRID

Fine MP-grid of phonon wavevectors (Integer Vector)
Phonon frequencies are calculated on a coarse set of wavevectors using DFPT and interpolated onto this finer grid of wavevectors.

PHONON_FINE_KPOINT_MP_OFFSET

Origin offset of the fine phonon MP grid (Real Vector)
The offset of the fine MP grid at which the phonons calculated using DFPT are interpolated.

PHONON_FINE_KPOINT_MP_SPACING

The spacing of points on the fine MP set for phonons (Physical)
This specifies the minimum spacing between points on a Monkhorst-Pack grid that phonons will be interpolated onto from the coarser phonon grid.

PHONON_FINE_KPOINT_PATH

Path of phonon wavevectors on a fine scale (Block)
Phonon frequencies are calculated on a coarse set of wavevectors using DFPT and interpolated onto this finer path.

PHONON_FINE_KPOINT_PATH_SPACING

The fine spacing of points on a path at which phonons are calculated (Physical)
The spacing of k-points along a path (specified by PHONON_FINE_KPOINT_PATH) at which phonons will be interpolated from a coarser grid

PHONON_GAMMA_DIRECTIONS

Phonon gamma-point LO/TO splitting (Block)
This is a list of directions along which ${\mathbf{q}}\rightarrow 0$ will be calculated for the non-analytic LO/TO term in a phonon calculation at ${\mathbf{q}}=0$. Fractional coordinates must be used. Default value: The k-point before gamma in the k-point list, or the one after or (0.1, 0, 0)

PHONON_KPOINTS_LIST

Alias for PHONON_KPOINT_LIST (Block)
Default value: Determined from PHONON_KPOINT_LIST

PHONON_KPOINTS_PATH

Alias for PHONON_KPOINT_PATH (Block)
Default value: Determined from PHONON_KPOINT_PATH

PHONON_KPOINTS_PATH_SPACING

Alias for PHONON_KPOINT_PATH_SPACING (Physical)
Default value: Determined from PHONON_KPOINT_PATH_SPACING

PHONON_KPOINT_LIST

List of phonon k-points (Block)
A list of discrete k-points at which phonon frequencies and eigenvectors will be calculated. Default value: SCF k-points are used if an alternative PHONON_KPOINT_* specifier is not given.

PHONON_KPOINT_MP_GRID

Phonon wavevector Monkhorst-Pack grid (Integer Vector)
The phonon wavevectors defined by a Monkhorst-Pack grid. Symmetry (if specified) will be used to generate the wavevector list and weights.

PHONON_KPOINT_MP_OFFSET

Phonon wavevector Monkhorst Pack grid offset (Real Vector)
The offset of the origin of the Monkhorst-Pack set for phonons in fractional coordinates, or the keyword INCLUDE_GAMMA. Default value: INCLUDE_GAMMA

PHONON_KPOINT_MP_SPACING

Phonon wavevector Monkhorst-Pack grid density (Physical)
The density of wavevectors on a a Monkhorst-Pack grid for phonon calculations. Units of inverse length should be specified. Default value: 0.1 A$^{-1}$.

PHONON_KPOINT_PATH

Phonon dispersion k-point path (Block)
The path continuous through the BZ on which phonon dispersion is calculated. This is specified in fractional coordinates. Default value: None.

PHONON_KPOINT_PATH_SPACING

Phonon dispersion path spacing (Physical)
The maximum spacing between kpoints along the path specified by PHONON_KPOINT_PATH. Units of inverse length must be specified. Default value: 0.1 A$^{-1}$.

PHONON_SUPERCELL_MATRIX

Supercell matrix for finite difference phonon calculations (Block)
The supercelling matrix for force constant matrix calculations. The supercell matrix is specified by a 3x3 integer matrix which gives the supercell used in finite-difference phonon calculations.

SUPERCELL_KPOINTS_LIST

SCF k-points for FD phonon supercell (Block)
A list of k-points in the Brillouin zone (with associated weights) used for BZ integration during a supercell FD phonon calculation. The k-point weights must sum to 1. Default value: Generated from SUPERCELL_KPOINTS_MP_SPACING and the crystal symmetry.

SUPERCELL_KPOINTS_MP_GRID

SCF Monkhorst-Pack grid for FD phonon supercell calculation (Integer Vector)
The k-points defined by a Monkhorst-Pack grid when doing a finite displacement phonon calculation. Symmetry (if specified) will be used to generate the k-point list and weights. Default value: Generated from SUPERCELL_KPOINTS_MP_SPACING.

SUPERCELL_KPOINTS_MP_OFFSET

SCF Monkhorst Pack grid offset for a FD phonon supercell calculation (Real Vector)
The offset of the origin of the Monkhorst-Pack set in fractional coordinates when performing a finite displacement phonon calculation. Default value: (0, 0, 0).

SUPERCELL_KPOINTS_MP_SPACING

SCF Monkhorst-Pack grid density for FD phonon supercell calculation (Physical)
The k-point density of a Monkhorst-Pack grid for a supercell FD phonon calculation. Units of inverse length should be specified. Default value: 0.1 A$^{-1}$.

PARAM file keywords

NUM_BACKUP_ITER

md/geom iterations between backups (Integer)
Specifies the number of iterations between backups of all data for restarts, for a geometry optimization or molecular dynamics run. Allowed values: (any integer) $>$ 0 Default value : 5

BACKUP_INTERVAL

seconds between backups (Integer)
Specifies the interval, in seconds, between backups of all data for restarts, for a geometry optimization/molecular dynamics/phonon run - if less than or equal to zero then no timed backups. Allowed values: (any) Default value : 0

BORN_CHARGE_SUM_RULE

enforce Born charge sum rule (Logical)
Selects whether to explicitly correct the Born effective charge tensor to enforce the sum rule that effective charges sum to zero.

CALCULATE_BORN_CHARGES

calculate Born effective charges (Logical)
Selects whether to compute Born effective charge tensors as part of a phonon or E-field linear-response calculation. Allowed values: TRUE or FALSE Default value : TRUE

CALCULATE_RAMAN

calculate Raman intensities (Logical)
Selects whether to compute Raman intensities as part of a phonon or E-field linear-response calculation. Allowed values: TRUE or FALSE Default value : FALSE

EFIELD_CALC_ION_PERMITTIVITY

calculate zero-frequency permittivity (Logical)
Specifies whether or not to compute the zero-frequency dielectric permittivity based on the ionic response to electric fields. This requires a gamma-point phonon calculation in addition to the EFIELD linear response one. Allowed values: TRUE or FALSE Default value : TRUE

EFIELD_CALCULATE_NONLINEAR

calculate non-linear optical susceptibility (String)
Select which non-linear optical property to calculate during TASK=EFIELD calculation. Allowed values: NONE, CHI2 Default value : NONE

EFIELD_CONVERGENCE_WIN

convergence tolerance window in EFIELD (Integer)
The LR convergence criteria must be met for EFIELD_CONVERGENCE_WIN iterations before acceptance. Allowed values: (any integer) $\ge$ 2 Default value : 2

EFIELD_DFPT_METHOD

E-field DFPT solver method (String)
Selects the solver for E-field density functional perturbation theory.. Allowed values: ALLBANDS(=VARIATIONAL) or DM(=GREEN) to select Gonze variational or Baroni Green function with DM solver. Default value : ALLBANDS

EFIELD_ENERGY_TOL

E(2) convergence tolerance in EFIELD (Physical)
Tolerance for accepting convergence of the field constants during PHONON calculation. The difference between max and min E(2) values over EFIELD_CONVERGENCE_WIN iterations must be less than this. NB This is an INTENSIVE parameter and has units of volume. Allowed values: (any) $>$ 0.0 Default value : $10^{-5}$ A$^3$

EFIELD_FREQ_SPACING

Spacing of frequencies in permittivity calculation (Physical)
Spacing of frequencies in calculation of frequency-dependent permittivity. Allowed values: (any) $>$ 0.0 Default value : 1.0 cm$^{-1}$

EFIELD_IGNORE_MOLEC_MODES

Ignore lowest modes in permittivity calculation (String)
Ignore the lowest lying (3,5,6) modes when computing the ionic contribution to the permittivity and polarizability. Allowed values: CRYSTAL, MOLECULE, LINEAR_MOLECULE Default value : CRYSTAL

EFIELD_MAX_CG_STEPS

max. number of cg steps in EFIELD (Integer)
The maximum number of conjugate gradient steps in EFIELD calculation before performing a SD reset. Allowed values: (any integer) $\ge$ 0 Default value : 0

EFIELD_MAX_CYCLES

maximum cycles in EFIELD (Integer)
The maximum number of SCF cycles in EFIELD calculation regardless of convergence. Allowed values: (any integer) $>$ 0 Default value : 50

EFIELD_OSCILLATOR_Q

Q-factor for line-shape broadening (Real)
Oscillator Q-factor for line-shape broadening in calculation of frequency- dependent permittivity. Allowed values: (any) $>$ 0.0 Default value : 50.0

EFIELD_UNIT

unit of electric field in output (String)
Controls the units used for all electric field in output - many different units are supported. Default value : eV/A/E

ELEC_METHOD

treatment of metals or finite temperature insulator (String)
The treatment of metals or finite temperature insulator to be used. An alias for METALS_METHOD. Allowed values: NONE (=ALLBANDS), DM, EDFT Default value : DM

EXCITED_STATE_SCISSORS

“scissors” operator band-gap correction (Physical)
Effectively adds an offset to conduction-band eigenvalues as empirical correction for LDA/GGA underestimation of band-gaps. Allowed values: (any) Default value : 0.0

FIX_OCCUPANCY

treat system as an insulator (Logical)
Determines if the system is treated as an insulator or a metal. Allowed values: TRUE or FALSE Default value : FALSE

GEOM_FORCE_TOL

geometry optimization force convergence tolerance (Physical)
Tolerance for accepting convergence of the maximum |ionic force| during geometry optimization. Allowed values: (any) $>$ 0.0 Default value : 0.05 eV/A

PHONON_CALCULATE_DOS

density of states calculation (Logical)
Determines whether or not the phonon density of states will be calculated. Allowed values: TRUE or FALSE Default value : FALSE

PHONON_DOS_SPACING

density of states calculation (Physical)
The resolution at which a phonon density-of-states will be calculated. Allowed values: (any) $> 0.0$ Default value : 10.0 cm$^{-1}$.

PHONON_DOS_LIMIT

density of states calculation (Logical)
The largest phonon to be included in a phonon density-of-states calculation. Allowed values: (any) $>$ PHONON_DOS_SPACING Default value : 5000.0 cm$^{-1}$.

PHONON_CALC_LO_TO_SPLITTING

gamma-point phonon LO/TO correction (Logical)
Selects whether to compute non-analytic contribution to dynamical matrix from long-ranged electric field effects responsible for LO/TO splitting. This requires calculation of the dielectric permittivity by E-field linear-response and the Born effective charges. Allowed values: TRUE or FALSE Default value : TRUE

PHONON_CONVERGENCE_WIN

convergence tolerance window in LR (Integer)
The LR convergence criteria must be met for PHONON_CONVERGENCE_WIN iterations before acceptance. Allowed values: (any integer) $\ge$ 2 Default value : 2

PHONON_ENERGY_TOL

E(2) convergence tolerance in LR (Physical)
Tolerance for accepting convergence of the force constants during PHONON calculation. The difference between max and min E(2) values over PHONON_CONVERGENCE_WIN iterations must be less than this. Allowed values: (any) $>$ 0.0 Default value : $10^{-5}$ eV/A$^2$

PHONON_FINE_METHOD

fine phonon calculation method (String)
Selects which calculation method to use for phonon calculation on a fine grid. Allowed values: NONE, SUPERCELL, INTERPOLATE Default value : SUPERCELL if TASK=THERMODYNAMICS else NONE

PHONON_FINITE_DISP

finite displacement amplitude (Physical)
The amplitude of the ionic perturbation to be used in a finite displacement phonon calculation. Allowed values: (any) $>$ 0.0 Default value : 0.01 $a_0$

PHONON_FORCE_CONSTANT_CUTOFF

Cutoff for force constant matrix (Physical)
The cutoff for the force constant matrix in a phonon calculation on a fine grid with supercell method. Allowed values: (any) $\ge$ 0.0 Default value : 0.0

PHONON_FINE_CUTOFF_METHOD

Selects which method to use to extract non-periodic force constant matrix from periodic supercell. (String)
With the CUMULANT method, all contributions from the periodic supercell are summed with a suitable weighting factor to avoid double counting of image contributions.
The SPHERICAL method, uses a minimum image convention with a spherical cutoff given by PHONON_FORCE_CONSTANT_CUTOFF.
Allowed values: CUMULANT and SPHERICAL. Default value : CUMULANT.

PHONON_FORCE_CONSTANT_CUT_SCALE

Scaling factor for aspherical force constant matrix cutoff (Real)
The range of force constant terms included is up to s times halfway to the Wigner Seitz cell boundary. This parameter supplies the value of s. Allowed values: 0.0 $\le$ (any) $\ge$ 1.0 Default value : 0.0

PHONON_FORCE_CONSTANT_ELLIPSOID

Ellipsoid size for force constant matrix (Real)
Alias for PHONON_FORCE_CONSTANT_CUT_SCALE (deprecated).

PHONON_MAX_CG_STEPS

max. number of cg steps in LR (Integer)
The maximum number of conjugate gradient steps in PHONON calculation before performing a SD reset. Allowed values: (any integer) $\ge$ 0 Default value : 0

PHONON_MAX_CYCLES

maximum cycles in LR (Integer)
The maximum number of SCF cycles in PHONON calculation regardless of convergence. Allowed values: (any integer) $\ge$ 0 or if TASK=PHONON etc $\ge$ PHONON_CONVERGENCE_WIN Default value : 50

PHONON_METHOD

phonon calculation method (String)
Selects which calculation method to use for phonons. Allowed values: DFPT, LINEARRESPONSE, FINITEDISPLACEMENT Default value : set by PHONON_FINE_METHOD

PHONON_DFPT_METHOD

phonon DFPT solver method (String)
Selects the solver for phonon density functional perturbation theory.. Allowed values: ALLBANDS(=VARIATIONAL) or DM(=GREEN) to select Gonze variational or Baroni Green function with DM solver. Default value : DM if FIX_OCCUPANCY : FALSE, otherwise ALLBANDS

PHONON_PRECONDITIONER

scheme to use in LR (String)
The preconditioning scheme used by the CG minimiser in LR. Allowed values: RTPA, TPA, PS, NONE Default value : TPA

PHONON_SUM_RULE

enforce phonon sum rule (Logical)
Selects whether to explicitly correct the dynamical matrix to enforce the acoustic q=0 phonon sum rule, i.e. that 3 modes have zero frequency at q=0. Allowed values: TRUE or FALSE Default value : FALSE

PHONON_SUM_RULE_METHOD

select method to enforce phonon sum rule (String)
Selects a method to use when enforcing acoustic phonon sum rule. Allowed values: NONE : No sum-rule correction will be applied. RECIPROCAL : Correct dynamical matrix D(q) at each q using D(q=0). REALSPACE : Correct the real-space force constant matrix C(R). REAL-RECIP : Correct C(R) in realspace followed by D(q) in reciprocal space. MOLECULAR : Correct D(0) using rotational as well as translational sum-rule. MOLECULAR-1D : Correct D(0) for a linear molecule using rotational as well as translational sum-rule. Default value : RECIPROCAL

PHONON_USE_KPOINT_SYMMETRY

reduced or full kpoint set in LR (Logical)
Selects which k-point set to use For each phonon q-vector in LR: T => use the irreducible k-point set of the (reduced) symmetry, F => use the complete fully symmetric k-point set. Allowed values: TRUE or FALSE Default value : TRUE

PHONON_WRITE_FORCE_CONSTANTS

Write out real-space force constant matrix (Logical)
Selects whether to write out the real-space force constant matrix from a phonon supercell or interpolation calculation (to the <seedname>.castep file) for the case of PHONON_FINE_METHOD /= NONE. Allowed values: TRUE or FALSE Default value : FALSE

PHONON_WRITE_DYNAMICAL

Write out reciprocal space dynamical matrix (Logical)
Selects whether to write out the reciprocal space dynamical matrices from a phonon calculation (to the <seedname>.castep file). /= NONE. Allowed values: TRUE or FALSE Default value : FALSE

THERMO_T_NPOINTS

Number of points in temperature interval (Integer)
The number of points in the temperature interval for the thermodynamics calculation. Allowed values: (any integer) $\ge$ 1 Default value : 2 if THERMO_T_STOP /= THERMO_T_START or 1 otherwise

THERMO_T_SPACING

Temperature spacing (Physical)
The spacing between temperature values for the thermodynamics calculation. Allowed values: (any) $>$ (-epsilon) Default value : THERMO_T_STOP - THERMO_T_START

THERMO_T_START

Starting temperature (Physical)
The desired starting temperature for the thermodynamics calculation. Allowed values: (any) $>$ 0.0 Default value : 298 K

THERMO_T_STOP

Final temperature (Physical)
The desired final temperature for the thermodynamics calculation. Allowed values: (any) $\ge$ THERMO_T_START Default value : 298