Phase Definitions#
A phase
is a mapping that contains definitions for the elements, species,
and optionally reactions that can take place in that phase. The fields of a
phase
entry are:
name
String identifier used for the phase. Required.
elements
Specification for the elements present in the phase. This can be:
Omitted, in which case the standard elements will be added as needed by the species included in the phase.
A list of element symbols, which can be either defined in the
elements
section of the file or taken from the standard elements.A list of single-key mappings of section names to lists of element symbols. These sections can be in the same file as the phase definition, or from another file if written as
file-path/sectionname
. If a relative path is specified, the directory containing the current file is searched first, followed by the Cantera data path. Standard elements can be included by referencing the fictitious sectiondefault
.
species
Specification for the species present in the phase. This can be:
a list of species that appear in the
species
section of the file.The string
all
, to indicate that all species in thespecies
section should be included. This is the default if nospecies
entry is present.A list of single-key mappings of section names to either the string
all
or a list of species names. These sections can be in the same file as the phase definition, or from another file if written asfile-path/sectionname
. If a relative path is specified, the directory containing the current file is searched first, followed by the Cantera data path.
Species may be skipped depending on the setting of the
skip-undeclared-elements
option.skip-undeclared-elements
If set to
true
, do not add species that contain elements that are not explicitly included in the phase. The default isfalse
, where the presence of such species is considered an error.skip-undeclared-third-bodies
If set to
true
, ignore third body efficiencies for species that are not defined in the phase. The default isfalse
, where the presence of such third body specifications is considered an error.
explicit-third-body-duplicates
Specifies how to handle three body reactions with an explicit collider that are duplicates of a three body reaction with the default collider
M
. This can be:warn
: Issue a warning about such reactions. This is the default.error
: Raise an exception if such reactions are found.mark-duplicate
: Mark the reactions as duplicates. Species production and consumption rates will reflect the sum of the rates. This option may correspond to the behavior of software packages that do not check for this kind of duplicate reaction.modify-efficiency
: Set the efficiency of the explicit third body to zero for the reaction that gives the rate for the default collider. This option is the most self-consistent but may not correspond to the intent of the mechanism’s authors.Added in version 3.1.
state
A mapping specifying the thermodynamic state. See Setting the state.
adjacent-phases
For interface phases, specification of adjacent phases that participate in reactions on the interface. This can be:
a list of phase names that appear in the
phases
section of the file.A list of single-key mappings of section names to a list of phase names. These sections can be in the same file as the current phase definition, or from another file if written as
file-path/section-name
. If a relative path is specified, the directory containing the current file is searched first, followed by the Cantera data path.
thermo
String specifying the phase thermodynamic model to be used. Supported model strings are:
binary-solution-tabulated
(details)compound-lattice
(details)coverage-dependent-surface
(details)Debye-Huckel
(details)edge
(details)electron-cloud
(details)fixed-stoichiometry
(details)HMW-electrolyte
(details)ideal-gas
(details)ideal-molal-solution
(details)ideal-condensed
(details)ideal-solution-VPSS
(details)ideal-surface
(details)lattice
(details)liquid-water-IAPWS95
(details)Margules
(details)Peng-Robinson
(details)plasma
(details)pure-fluid
(details)Redlich-Kister
(details)Redlich-Kwong
(details)
kinetics
String specifying the kinetics model to be used. Supported model strings are:
reactions
Source of reactions to include in the phase, if a kinetics model has been specified. This can be:
The string
all
, which indicates that all reactions from thereactions
section of the file should be included. This is the default if noreactions
entry is present.The string
declared-species
, which indicates that all reactions from thereactions
section involving only species present in the phase should be included.The string
none
, which indicates that no reactions should be added. This can be used if reactions will be added programmatically after the phase is constructed.A list of sections from which to include reactions. These sections can be in the same file as the phase definition, or from another file if written as
file-path/sectionname
. If a relative path is specified, the directory containing the current file is searched first, followed by the Cantera data path.A list of single-key mappings of section names to rules for adding reactions, where for each section name, that rule is either
all
ordeclared-species
and is applied as described above.
Motz-Wise
Boolean indicating whether the Motz-Wise correction should be applied to sticking reactions. Applicable only to interface phases. The default is
false
. The value set at the phase level may be overridden on individual reactions.
transport
String specifying the transport model to be used. Supported model strings are:
none
high-pressure
: A model for high-pressure gas transport properties based on a method of corresponding states (details)ionized-gas
: A model implementing the Stockmayer-(n,6,4) model for transport of ions in a gas (details)mixture-averaged
: The mixture-averaged transport model for ideal gases (details)mixture-averaged-CK
: The mixture-averaged transport model for ideal gases, using polynomial fits corresponding to Chemkin-II (details)multicomponent
: The multicomponent transport model for ideal gases (details)multicomponent-CK
: The multicomponent transport model for ideal gases, using polynomial fits corresponding to Chemkin-II (details)unity-Lewis-number
: A transport model for ideal gases, where diffusion coefficients for all species are set so that the Lewis number is 1 (details)water
: A transport model for pure water applicable in both liquid and vapor phases (details)
Setting the state#
The state of a phase
can be set using two properties to set the
thermodynamic state, plus the composition.
The composition can be set using one of the following fields, depending on the phase type. The composition is specified as a mapping of species names to values. Where necessary, the values will be automatically normalized.
mass-fractions
orY
mole-fractions
orX
coverages
molalities
orM
The thermodynamic state can be set using the following property pairs, with some exceptions for phases where setting that property pair is not implemented. All properties are on a per unit mass basis where relevant:
T
andP
T
andD
T
andV
H
andP
U
andV
S
andV
S
andP
S
andT
P
andV
U
andP
V
andH
T
andH
S
andH
D
andP
The following synonyms are also implemented for use in any of the pairs:
temperature
,T
pressure
,P
enthalpy
,H
entropy
,S
int-energy
,internal-energy
,U
specific-volume
,V
density
,D
Phase thermodynamic models#
binary-solution-tabulated
#
A phase representing a binary solution where the excess enthalpy and entropy are interpolated between tabulated values as a function of mole fraction, as described here.
Includes the fields of ideal-condensed, plus:
tabulated-species
The name of the species to which the tabulated enthalpy and entropy is added.
tabulated-thermo
A mapping containing three (optionally four) lists of equal lengths:
mole-fractions
A list of mole fraction values for the tabulated species.
enthalpy
The extra molar enthalpy to be added to the tabulated species at these mole fractions.
entropy
The extra molar entropy to be added to the tabulated species at these mole fractions.
molar-volume
The molar volume of the phase at these mole fractions. This input is optional.
Added in version 2.5.
compound-lattice
#
A phase that is comprised of a fixed additive combination of other lattice phases, as described here.
Additional fields:
composition
A mapping of component phase names to their relative stoichiometries.
Example:
thermo: compound-lattice
composition: {Li7Si3(s): 1.0, Li7Si3-interstitial: 1.0}
coverage-dependent-surface
#
A coverage-dependent surface phase. That is, a surface phase where the enthalpy, entropy, and heat capacity of each species may depend on its coverage and the coverage of other species in the phase. Full details are described here. The majority of coverage dependency parameters are provided in the species entry as described here.
Additional fields:
site-density
The molar density of surface sites.
reference-state-coverage
The reference state coverage denoting the low-coverage limit (ideal-surface) thermodynamic properties.
Example:
- name: covdep
thermo: coverage-dependent-surface
species: [Pt, OC_Pt, CO2_Pt, C_Pt, O_Pt]
state:
T: 500.0
P: 1.01325e+05
coverages: {Pt: 0.5, OC_Pt: 0.5, CO2_Pt: 0.0, C_Pt: 0.0, O_Pt: 0.0}
site-density: 2.72e-09
reference-state-coverage: 0.22
Added in version 3.0.
Debye-Huckel
#
A dilute liquid electrolyte which obeys the Debye-Hückel formulation for nonideality as
described here. Additional parameters for this model are contained
in the activity-data
field:
activity-data
The activity data field contains the following fields:
model
One of
dilute-limit
,B-dot-with-variable-a
,B-dot-with-common-a
,beta_ij
, orPitzer-with-beta_ij
A_Debye
The value of the Debye “A” parameter, or the string
variable
to use a calculation based on the water equation of state. Defaults to the constant value of 1.172576 kg^0.5/gmol^0.5, a nominal value for water at 298 K and 1 atm.B_Debye
The Debye “B” parameter. Defaults to 3.2864e+09 kg^0.5/gmol^0.5/m, a nominal value for water.
max-ionic-strength
The maximum ionic strength
use-Helgeson-fixed-form
Boolean,
true
orfalse
default-ionic-radius
Ionic radius to use for species where the ionic radius has not been specified.
B-dot
The value of B-dot.
beta
List of mappings providing values of \(\beta_{ij}\) for different species pairs. Each mapping contains a
species
key that contains a list of two species names, and abeta
key that contains the corresponding value of \(\beta_{ij}\).
Example:
thermo: Debye-Huckel
activity-data:
model: beta_ij
max-ionic-strength: 3.0
use-Helgeson-fixed-form: true
default-ionic-radius: 3.042843 angstrom
beta:
- species: [H+, Cl-]
beta: 0.27
- species: [Na+, Cl-]
beta: 0.15
- species: [Na+, OH-]
beta: 0.06
In addition, the Debye-Hückel model uses several species-specific properties
which may be defined in the Debye-Huckel
field of the species entry. These
properties are:
ionic-radius
Size of the species.
electrolyte-species-type
One of
solvent
,charged-species
,weak-acid-associated
,strong-acid-associated
,polar-neutral
, ornonpolar-neutral
. The typesolvent
is the default for the first species in the phase. The typecharged-species
is the default for species with a net charge. Otherwise, the default is andnonpolar-neutral
.weak-acid-charge
Charge to use for species that can break apart into charged species.
Example:
name: NaCl(aq)
composition: {Na: 1, Cl: 1}
thermo:
model: piecewise-Gibbs
h0: -96.03E3 cal/mol
dimensionless: true
data: {298.15: -174.5057463, 333.15: -174.5057463}
equation-of-state:
model: constant-volume
molar-volume: 1.3
Debye-Huckel:
ionic-radius: 4 angstrom
electrolyte-species-type: weak-acid-associated
weak-acid-charge: -1.0
edge
#
A one-dimensional edge between two surfaces, as described here.
Additional fields:
site-density
The molar density of sites per unit length along the edge
Example:
thermo: edge
site-density: 5.0e-17 mol/cm
electron-cloud
#
A phase representing an electron cloud, such as conduction electrons in a metal, as described here.
Additional fields:
density
The density of the bulk metal
fixed-stoichiometry
#
An incompressible phase with fixed composition, as described here.
HMW-electrolyte
#
A dilute or concentrated liquid electrolyte phase that obeys the Pitzer formulation for nonideality, as described here.
Additional parameters for this model are contained in the activity-data
field:
activity-data
The activity data field contains the following fields:
temperature-model
The form of the Pitzer temperature model. One of
constant
,linear
orcomplex
. The default isconstant
.A_Debye
The value of the Debye “A” parameter, or the string
variable
to use a calculation based on the water equation of state. The default is 1.172576 kg^0.5/gmol^0.5, a nominal value for water at 298 K and 1 atm.max-ionic-strength
The maximum ionic strength
interactions
A list of mappings, where each mapping describes a binary or ternary interaction among species. Fields of this mapping include:
species
A list of one to three species names
beta0
The \(\beta^{(0)}\) parameters for an cation/anion interaction. 1, 2, or 5 values depending on the value of
temperature-model
.beta1
The \(\beta^{(1)}\) parameters for an cation/anion interaction. 1, 2, or 5 values depending on the value of
temperature-model
.beta2
The \(\beta^{(2)}\) parameters for an cation/anion interaction. 1, 2, or 5 values depending on the value of
temperature-model
.Cphi
The \(C^\phi\) parameters for an cation/anion interaction. 1, 2, or 5 values depending on the value of
temperature-model
.alpha1
The \(\alpha^{(1)}\) parameter for an cation/anion interaction.
alpha2
The \(\alpha^{(2)}\) parameter for an cation/anion interaction.
theta
The \(\theta\) parameters for a like-charged binary interaction. 1, 2, or 5 values depending on the value of
temperature-model
.lambda
The \(\lambda\) parameters for binary interactions involving at least one neutral species. 1, 2, or 5 values depending on the value of
temperature-model
.psi
The \(\Psi\) parameters for ternary interactions involving three charged species. 1, 2, or 5 values depending on the value of
temperature-model
.zeta
The \(\zeta\) parameters for ternary interactions involving one neutral species. 1, 2, or 5 values depending on the value of
temperature-model
.mu
The \(\mu\) parameters for a neutral species self-interaction. 1, 2, or 5 values depending on the value of
temperature-model
.
cropping-coefficients
ln_gamma_k_min
Default -5.0.
ln_gamma_k_max
Default 15.0.
ln_gamma_o_min
Default -6.0.
ln_gamma_o_max
Default 3.0.
Example:
thermo: HMW-electrolyte
activity-data:
temperature-model: complex
A_Debye: 1.175930 kg^0.5/gmol^0.5
interactions:
- species: [Na+, Cl-]
beta0: [0.0765, 0.008946, -3.3158E-6, -777.03, -4.4706]
beta1: [0.2664, 6.1608E-5, 1.0715E-6, 0.0, 0.0]
beta2: [0.0, 0.0, 0.0, 0.0, 0.0]
Cphi: [0.00127, -4.655E-5, 0.0, 33.317, 0.09421]
alpha1: 2.0
- species: [H+, Cl-]
beta0: [0.1775]
beta1: [0.2945]
beta2: [0.0]
Cphi: [0.0008]
alpha1: 2.0
- species: [Na+, OH-]
beta0: 0.0864
beta1: 0.253
beta2: 0.0
Cphi: 0.0044
alpha1: 2.0
alpha2: 0.0
- {species: [Cl-, OH-], theta: -0.05}
- {species: [Na+, Cl-, OH-], psi: -0.006}
- {species: [Na+, H+], theta: 0.036}
- {species: [Cl-, Na+, H+], psi: [-0.004]}
ideal-gas
#
A mixture which obeys the ideal gas law, as described here.
Example:
- name: ohmech
thermo: ideal-gas
elements: [O, H, Ar, N]
species: [H2, H, O, O2, OH, H2O, HO2, H2O2, AR, N2]
kinetics: gas
transport: mixture-averaged
state: {T: 300.0, P: 1 atm}
ideal-molal-solution
#
An ideal solution based on the mixing-rule assumption that all molality-based activity coefficients are equal to one, as described here.
Additional fields:
standard-concentration-basis
A string specifying the basis for the standard concentration. One of
unity
,species-molar-volume
, orsolvent-molar-volume
.cutoff
Parameters for cutoff treatments of activity coefficients
model
poly
orpolyExp
gamma_o
gamma_o value for the cutoff process at the zero solvent point
gamma_k
gamma_k minimum for the cutoff process at the zero solvent point
X_o
value of the solute mole fraction that centers the cutoff polynomials for the cutoff = 1 process
c_0
Parameter in the polyExp cutoff treatment having to do with rate of exponential decay
slope_f
Parameter in the
polyExp
cutoff treatmentslope_g
Parameter in the
polyExp
cutoff treatment
Example:
thermo: ideal-molal-solution
standard-concentration-basis: solvent-molar-volume
cutoff:
model: polyexp
gamma_o: 0.0001
gamma_k: 10.0
X_o: 0.2
c_0: 0.05
slope_f: 0.6
slope_g: 0.0
ideal-condensed
#
An ideal liquid or solid solution as described here.
Additional fields:
standard-concentration-basis
A string specifying the basis for the standard concentration. One of
unity
,species-molar-volume
, orsolvent-molar-volume
.
ideal-solution-VPSS
#
An ideal solution model using variable pressure standard state methods as described here.
Additional fields:
standard-concentration-basis
A string specifying the basis for the standard concentration. One of
unity
,species-molar-volume
, orsolvent-molar-volume
.
ideal-surface
#
An ideal surface between two bulk phases, as described here.
Additional fields:
site-density
The molar density of surface sites
Example:
- name: Pt_surf
thermo: ideal-surface
adjacent-phases: [gas]
elements: [Pt, H, O, C]
species: [PT(S), H(S), H2O(S), OH(S), CO(S), CO2(S), CH3(S), CH2(S)s,
CH(S), C(S), O(S)]
kinetics: surface
reactions: all
state:
T: 900.0
coverages: {O(S): 0.0, PT(S): 0.5, H(S): 0.5}
site-density: 2.7063e-09
lattice
#
A simple thermodynamic model for a bulk phase, assuming an incompressible lattice of solid atoms, as described here.
Additional fields:
site-density
The molar density of lattice sites
liquid-water-IAPWS95
#
An implementation of the IAPWS95 equation of state for water [Wagner and Pruß, 2002], for the liquid region only as described here.
Margules
#
A phase employing the Margules approximation for the excess Gibbs free energy, as described here.
Additional fields:
interactions
A list of mappings, where each mapping has the following fields:
species
A list of two species names
excess-enthalpy
A list of two values specifying the first and second excess enthalpy coefficients for the interaction of the specified species. Defaults to [0, 0].
excess-entropy
A list of two values specifying the first and second excess entropy coefficients for the interaction of the specified species. Defaults to [0, 0].
excess-volume-enthalpy
A list of two values specifying the first and second enthalpy coefficients for the excess volume interaction of the specified species. Defaults to [0, 0].
excess-volume-entropy
A list of two values specifying the first and second entropy coefficients for the excess volume interaction of the specified species. Defaults to [0, 0].
Example:
thermo: Margules
interactions:
- species: [KCl(l), LiCl(l)]
excess-enthalpy: [-17570, -377]
excess-entropy: [-7.627, 4.958]
Peng-Robinson
#
A multi-species real gas following the Peng-Robinson equation of state, as described here.
The parameters for each species are contained in the corresponding species entries. See Peng-Robinson species equation of state.
Added in version 3.0.
plasma
#
A phase for plasma. This phase handles plasma properties such as the electron energy distribution and electron temperature with different models as described here.
Additional fields:
electron-energy-distribution
A mapping with the following fields:
type
String specifying the type of the electron energy distribution to be used. Supported model strings are:
isotropic
discretized
shape-factor
A constant in the isotropic distribution, which is shown as x in the detailed description of this class. The value needs to be a positive number. This field is only used with
isotropic
. Defaults to 2.0.mean-electron-energy
Mean electron energy of the isotropic distribution. The default sets the electron temperature equal gas temperature and uses the corresponding electron energy as mean electron energy. This field is only used with
isotropic
.energy-levels
A list of values specifying the electron energy levels. The default uses 1001 equal spaced points from 0 to 1 eV.
distribution
A list of values specifying the discretized electron energy distribution. This field is only used with
discretized
.normalize
A flag specifying whether normalizing the discretized electron energy distribution or not. This field is only used with
discretized
. Defaults totrue
.
Example:
- name: isotropic-electron-energy-plasma
thermo: plasma
kinetics: gas
transport: ionized-gas
electron-energy-distribution:
type: isotropic
shape-factor: 2.0
mean-electron-energy: 1.0 eV
energy-levels: [0.0, 0.1, 1.0, 10.0]
- name: discretized-electron-energy-plasma
thermo: plasma
kinetics: gas
transport: ionized-gas
electron-energy-distribution:
type: discretized
energy-levels: [0.0, 0.1, 1.0, 10.0]
distribution: [0.0, 0.2, 0.7, 0.01]
normalize: False
Added in version 2.6.
pure-fluid
#
A phase representing a pure fluid equation of state for one of several pure substances including liquid, vapor, two-phase, and supercritical regions, as described here.
Additional fields:
pure-fluid-name
Name of the pure fluid model to use: -
carbon-dioxide
-heptane
-HFC-134a
-hydrogen
-methane
-nitrogen
-oxygen
-water
Redlich-Kister
#
A phase employing the Redlich-Kister approximation for the excess Gibbs free energy, as described here.
Additional fields:
interactions
A list of mappings, where each mapping has the following fields:
species
A list of two species names
excess-enthalpy
A list of polynomial coefficients for the excess enthalpy of the specified binary interaction
excess-entropy
A list of polynomial coefficients for the excess entropy of the specified binary interaction
Example:
thermo: Redlich-Kister
interactions:
- species: [Li(C6), V(C6)]
excess-enthalpy: [-3.268e+06, 3.955e+06, -4.573e+06, 6.147e+06, -3.339e+06,
1.117e+07, 2.997e+05, -4.866e+07, 1.362e+05, 1.373e+08,
-2.129e+07, -1.722e+08, 3.956e+07, 9.302e+07, -3.280e+07]
excess-entropy: [0.0]
Redlich-Kwong
#
A multi-species Redlich-Kwong phase as described here.
The parameters for each species are contained in the corresponding species entries. See Redlich-Kwong species equation of state.