The cell and param file keywords used specifically for phonon and related calculations are listed here alphabetically with brief descriptions.
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\(^{-1}\).
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