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# 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:

  - binary-solution-tabulated

  - compound-lattice

  - constant-density

  - Debye-Huckel

  - edge

  - electron-cloud

  - fixed-stoichiometry

  - HMW-electrolyte

  - ideal-gas

  - ideal-molal-solution

  - ideal-condensed

  - ideal-solution-VPSS

  - ideal-surface

  - ions-from-neutral-molecule

  - lattice

  - liquid-water-IAPWS95

  - Margules

  - Maskell-solid-solution

  - Peng-Robinson

  - plasma

  - pure-fluid

  - Redlich-Kister

  - Redlich-Kwong

`kinetics`

  String specifying the kinetics model to be used. Supported model strings are:

  - none

  - gas

  - surface

  - edge

`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

  - ionized-gas

  - mixture-averaged

  - mixture-averaged-CK

  - multicomponent

  - multicomponent-CK

  - unity-Lewis-number

  - water

## 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.

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}

### `constant-density`

An incompressible phase with constant density, as described here.

Additional fields:

`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
      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

### `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.

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`

A condensed phase ideal 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 phase, as described here.

Additional fields:

`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.

Additional fields:

`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.

Additional fields:

`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.

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]

### `Maskell-solid-solution`

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

Additional fields:

`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.

Additional fields:

`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.

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.

### `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.

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: 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