# 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.

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:

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 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:

## 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 implementing tabulated standard state thermodynamics for one species in a binary solution, as described here.

Includes the fields of ideal-molal-solution, 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.

### compound-lattice¶

A phase that is comprised of a fixed additive combination of other lattice phases, as described here.

composition

A mapping of component phase names to their relative stoichiometries.

Example:

thermo: compound-lattice
composition: {Li7Si3(s): 1.0, Li7Si3-interstitial: 1.0}


### constant-density¶

An incompressible phase with constant density, as described here.

density

The density of the phase

Example:

thermo: constant-density
density: 0.7 g/cm^3


### Debye-Huckel¶

The Debye-Hückel model 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.

B_Debye

The Debye “B” parameter

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
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:
electrolyte-species-type: weak-acid-associated
weak-acid-charge: -1.0


### edge¶

A one-dimensional edge between two surfaces, as described here.

site-density

The molar density of sites per unit length along the edge

Example:

thermo: edge
site-density: 5.0e-17 mol/cm


### fixed-stoichiometry¶

A 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.

A_Debye

The value of the Debye “A” parameter, or the string variable to use a calculation based on the water equation of state.

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¶

The ideal gas model as described here.

### ideal-molal-solution¶

A phase based on the mixing-rule assumption that all molality-based activity coefficients are equal to one, as described here.

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¶

A condensed phase ideal solution as described here.

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.

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 phase, as described here.

site-density

The molar density of surface sites

### ions-from-neutral-molecule¶

A model that handles the specification of the chemical potentials for ionic species, given a specification of the chemical potentials for the same phase expressed in terms of combinations of the ionic species that represent neutral molecules, as described here.

neutral-phase

The name of the phase definition for the phase containing the neutral molecules.

Example:

- name: KCl-ions
thermo: ions-from-neutral-molecule
neutral-phase: KCl-neutral
species: [K+, Cl-]
- name: KCl-neutral
species: [KCl(l)]
thermo: Margules


### lattice¶

A simple thermodynamic model for a bulk phase, assuming a lattice of solid atoms, as described here.

site-density

The molar density of lattice sites

### liquid-water-IAPWS95¶

An equation of state for liquid water, as described here.

### Margules¶

A phase employing the Margules approximation for the excess Gibbs free energy, as described here.

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]


### Maskell-solid-solution¶

A condensed phase non-ideal solution with two species, as described here.

excess-enthalpy

The molar excess enthalpy

product-species

String specifying the “product” species

Example:

thermo: Maskell-solid-solution
excess-enthalpy: 5 J/mol
product-species: H(s)


### electron-cloud¶

A phase representing an electron cloud, such as conduction electrons in a metal, as described here.

density

The density of the bulk metal

### pure-fluid¶

A phase representing a pure fluid equation of state for one of several species, as described here.

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.

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.

### Peng-Robinson¶

A multi-species Peng-Robinson phase as described here.

The parameters for each species are contained in the corresponding species entries.

### 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.

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: Ion
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: Ion
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