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 section default.

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 the species section should be included. This is the default if no species 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 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.

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 is false, 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 is false, 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:

none
bulk (details)
gas (alias for bulk)
surface (details)
edge (details)

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 the reactions section of the file should be included. This is the default if no reactions entry is present.
The string declared-species, which indicates that all reactions from the reactions 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 or declared-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 or Y
mole-fractions or X
coverages
molalities or M

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 and P
T and D
T and V
H and P
U and V
S and V
S and P
S and T
P and V
U and P
V and H
T and H
S and H
D and P

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, or Pitzer-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 or false
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 a beta 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, or nonpolar-neutral. The type solvent is the default for the first species in the phase. The type charged-species is the default for species with a net charge. Otherwise, the default is and nonpolar-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 or complex. The default is constant.

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, or solvent-molar-volume.

cutoff

Parameters for cutoff treatments of activity coefficients

model: poly or polyExp
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 treatment
slope_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, or solvent-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, or solvent-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 to true.

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.

Phase Definitions#

Setting the state#

Phase thermodynamic models#

binary-solution-tabulated#

compound-lattice#

coverage-dependent-surface#

Debye-Huckel#

edge#

electron-cloud#

fixed-stoichiometry#

HMW-electrolyte#

ideal-gas#

ideal-molal-solution#

ideal-condensed#

ideal-solution-VPSS#

ideal-surface#

lattice#

liquid-water-IAPWS95#

Margules#

Peng-Robinson#

plasma#

pure-fluid#

Redlich-Kister#

Redlich-Kwong#

`binary-solution-tabulated`#

`compound-lattice`#

`coverage-dependent-surface`#

`Debye-Huckel`#

`edge`#

`electron-cloud`#

`fixed-stoichiometry`#

`HMW-electrolyte`#

`ideal-gas`#

`ideal-molal-solution`#

`ideal-condensed`#

`ideal-solution-VPSS`#

`ideal-surface`#

`lattice`#

`liquid-water-IAPWS95`#

`Margules`#

`Peng-Robinson`#

`plasma`#

`pure-fluid`#

`Redlich-Kister`#

`Redlich-Kwong`#