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# Chemical Kinetics

- Kinetics Managers

  - Kinetics

  - InterfaceKinetics

- Reactions

  - Reaction

  - ElementaryReaction

  - ThreeBodyReaction

  - FalloffReaction

  - ChemicallyActivatedReaction

  - PlogReaction

  - ChebyshevReaction

  - InterfaceReaction

- Reaction Rates

  - ReactionRate

  - ArrheniusRateBase

  - ArrheniusRate

  - BlowersMaselRate

  - TwoTempPlasmaRate

  - FalloffRate

  - LindemannRate

  - TroeRate

  - SriRate

  - TsangRate

  - PlogRate

  - ChebyshevRate

  - CustomRate

  - InterfaceRateBase

  - InterfaceArrheniusRate

  - InterfaceBlowersMaselRate

  - StickRateBase

  - StickingArrheniusRate

  - StickingBlowersMaselRate

- Auxiliary Reaction Data (legacy only)

  - Arrhenius

  - Falloff

  - TroeFalloff

  - SriFalloff

- Reaction Path Analysis

  - ReactionPathDiagram

## Kinetics Managers

### Kinetics

class cantera.Kinetics(*args, **kwargs)

  Bases: `_SolutionBase`

  Instances of class `Kinetics` are responsible for evaluating reaction rates of progress, species production rates, and other quantities pertaining to a reaction mechanism.

  add_reaction(self, Reaction rxn)

    Add a new reaction to this phase.

  creation_rates

    Creation rates for each species. [kmol/m^3/s] for bulk phases or [kmol/m^2/s] for surface phases.

  creation_rates_ddC

    Calculate derivatives of species creation rates with respect to molar concentration at constant temperature, pressure and mole fractions.

    Warning: this property is an experimental part of the Cantera API and may be changed or removed without notice.

  creation_rates_ddP

    Calculate derivatives of species creation rates with respect to pressure at constant temperature, molar concentration and mole fractions.

  creation_rates_ddT

    Calculate derivatives of species creation rates with respect to temperature at constant pressure, molar concentration and mole fractions.

  creation_rates_ddX

    Calculate derivatives for species creation rates with respect to species concentrations at constant temperature, pressure and molar concentration. For sparse output, set `ct.use_sparse(True)`.

    Note that for derivatives with respect to \(X_i\), all other \(X_j\) are held constant, rather than enforcing \(\sum X_j = 1\).

    Warning: this property is an experimental part of the Cantera API and may be changed or removed without notice.

  delta_enthalpy

    Change in enthalpy for each reaction [J/kmol].

  delta_entropy

    Change in entropy for each reaction [J/kmol/K].

  delta_gibbs

    Change in Gibbs free energy for each reaction [J/kmol].

  delta_standard_enthalpy

    Change in standard-state enthalpy (independent of composition) for each reaction [J/kmol].

  delta_standard_entropy

    Change in standard-state entropy (independent of composition) for each reaction [J/kmol/K].

  delta_standard_gibbs

    Change in standard-state Gibbs free energy (independent of composition) for each reaction [J/kmol].

  derivative_settings

    Property setting behavior of derivative evaluation.

    For `GasKinetics`, the following keyword/value pairs are supported:

    - `skip-third-bodies` (boolean) … if `False` (default), third body concentrations are considered for the evaluation of derivatives

    - `skip-falloff` (boolean) … if `True` (default), third-body effects on reaction rates are not considered.

    - `rtol-delta` (double) … relative tolerance used to perturb properties when calculating numerical derivatives. The default value is 1e-8.

    Derivative settings are updated using a dictionary:

        >>> gas.derivative_settings = {"skip-falloff": True}

    Passing an empty dictionary will reset all values to their defaults.

  destruction_rates

    Destruction rates for each species. [kmol/m^3/s] for bulk phases or [kmol/m^2/s] for surface phases.

  destruction_rates_ddC

    Calculate derivatives of species destruction rates with respect to molar concentration at constant temperature, pressure and mole fractions.

    Warning: this property is an experimental part of the Cantera API and may be changed or removed without notice.

  destruction_rates_ddP

    Calculate derivatives of species destruction rates with respect to pressure at constant temperature, molar concentration and mole fractions.

  destruction_rates_ddT

    Calculate derivatives of species destruction rates with respect to temperature at constant pressure, molar concentration and mole fractions.

  destruction_rates_ddX

    Calculate derivatives for species destruction rates with respect to species concentrations at constant temperature, pressure and molar concentration. For sparse output, set `ct.use_sparse(True)`.

    Note that for derivatives with respect to \(X_i\), all other \(X_j\) are held constant, rather than enforcing \(\sum X_j = 1\).

    Warning: this property is an experimental part of the Cantera API and may be changed or removed without notice.

  equilibrium_constants

    Equilibrium constants in concentration units for all reactions.

  forward_rate_constants

    Forward rate constants for all reactions. The computed values include all temperature-dependent, pressure-dependent, and third body contributions. Units are a combination of kmol, m^3 and s, that depend on the rate expression for the reaction.

    Deprecated since version 2.6: Behavior to change after Cantera 2.6; for Cantera 2.6, rate constants of three-body reactions are multiplied with third-body concentrations (no change to legacy behavior). After Cantera 2.6, results will no longer include third-body concentrations and be consistent with conventional definitions (see Eq. 9.75 in Kee, Coltrin, and Glarborg, Chemically Reacting Flow, Wiley Interscience, 2003). To switch to new behavior, run `ct.use_legacy_rate_constants(False)`.

  forward_rate_constants_ddC

    Calculate derivatives for forward rate constants with respect to molar concentration at constant temperature, pressure and mole fractions.

    Warning: this property is an experimental part of the Cantera API and may be changed or removed without notice.

  forward_rate_constants_ddP

    Calculate derivatives for forward rate constants with respect to pressure at constant temperature, molar concentration and mole fractions.

  forward_rate_constants_ddT

    Calculate derivatives for forward rate constants with respect to temperature at constant pressure, molar concentration and mole fractions.

  forward_rates_of_progress

    Forward rates of progress for the reactions. [kmol/m^3/s] for bulk phases or [kmol/m^2/s] for surface phases.

  forward_rates_of_progress_ddC

    Calculate derivatives for forward rates-of-progress with respect to molar concentration at constant temperature, pressure and mole fractions.

    Warning: this property is an experimental part of the Cantera API and may be changed or removed without notice.

  forward_rates_of_progress_ddP

    Calculate derivatives for forward rates-of-progress with respect to pressure at constant temperature, molar concentration and mole fractions.

  forward_rates_of_progress_ddT

    Calculate derivatives for forward rates-of-progress with respect to temperature at constant pressure, molar concentration and mole fractions.

  forward_rates_of_progress_ddX

    Calculate derivatives for forward rates-of-progress with respect to species concentrations at constant temperature, pressure and molar concentration. For sparse output, set `ct.use_sparse(True)`.

    Note that for derivatives with respect to \(X_i\), all other \(X_j\) are held constant, rather than enforcing \(\sum X_j = 1\).

    Warning: this property is an experimental part of the Cantera API and may be changed or removed without notice.

  heat_production_rates

    Get the volumetric heat production rates [W/m^3] on a per-reaction basis. The sum over all reactions results in the total volumetric heat release rate. Example: C. K. Law: Combustion Physics (2006), Fig. 7.8.6

        >>> gas.heat_production_rates[1]  # heat production rate of the 2nd reaction

  heat_release_rate

    Get the total volumetric heat release rate [W/m^3].

  is_reversible(self, int i_reaction)

    True if reaction `i_reaction` is reversible.

    Deprecated since version 2.6: Replaced by property `Reaction.reversible`. Example: `gas.is_reversible(0)` is replaced by `gas.reaction(0).reversible`

  kinetics_model

    Return type of kinetics.

  kinetics_species_index(self, species, int phase=0)

    The index of species `species` of phase `phase` within arrays returned by methods of class `Kinetics`. If `species` is a string, the `phase` argument is unused.

  kinetics_species_name(self, k)

    Name of the species with index `k` in the arrays returned by methods of class `Kinetics`.

  kinetics_species_names

    A list of all species names, corresponding to the arrays returned by methods of class `Kinetics`.

  modify_reaction(self, int irxn, Reaction rxn)

    Modify the `Reaction` with index `irxn` to have the same rate parameters as `rxn`. `rxn` must have the same reactants and products and be of the same type (for example, `ElementaryReaction`, `FalloffReaction`, `PlogReaction`, etc.) as the existing reaction. This method does not modify the third-body efficiencies, reaction orders, or reversibility of the reaction.

  multiplier(self, int i_reaction)

    A scaling factor applied to the rate coefficient for reaction `i_reaction`. Can be used to carry out sensitivity analysis or to selectively disable a particular reaction. See `set_multiplier`.

  n_phases

    Number of phases in the reaction mechanism.

  n_reactions

    Number of reactions in the reaction mechanism.

  n_total_species

    Total number of species in all phases participating in the kinetics mechanism.

  net_production_rates

    Net production rates for each species. [kmol/m^3/s] for bulk phases or [kmol/m^2/s] for surface phases.

  net_production_rates_ddC

    Calculate derivatives of species net production rates with respect to molar density at constant temperature, pressure and mole fractions.

    Warning: this property is an experimental part of the Cantera API and may be changed or removed without notice.

  net_production_rates_ddP

    Calculate derivatives of species net production rates with respect to pressure at constant temperature, molar concentration and mole fractions.

  net_production_rates_ddT

    Calculate derivatives of species net production rates with respect to temperature at constant pressure, molar concentration and mole fractions.

  net_production_rates_ddX

    Calculate derivatives for species net production rates with respect to species concentrations at constant temperature, pressure and molar concentration. For sparse output, set `ct.use_sparse(True)`.

    Note that for derivatives with respect to \(X_i\), all other \(X_j\) are held constant, rather than enforcing \(\sum X_j = 1\).

    Warning: this property is an experimental part of the Cantera API and may be changed or removed without notice.

  net_rates_of_progress

    Net rates of progress for the reactions. [kmol/m^3/s] for bulk phases or [kmol/m^2/s] for surface phases.

  net_rates_of_progress_ddC

    Calculate derivatives for net rates-of-progress with respect to molar concentration at constant temperature, pressure and mole fractions.

    Warning: this property is an experimental part of the Cantera API and may be changed or removed without notice.

  net_rates_of_progress_ddP

    Calculate derivatives for net rates-of-progress with respect to pressure at constant temperature, molar concentration and mole fractions.

  net_rates_of_progress_ddT

    Calculate derivatives for net rates-of-progress with respect to temperature at constant pressure, molar concentration and mole fractions.

  net_rates_of_progress_ddX

    Calculate derivatives for net rates-of-progress with respect to species concentrations at constant temperature, pressure and molar concentration. For sparse output, set `ct.use_sparse(True)`.

    Note that for derivatives with respect to \(X_i\), all other \(X_j\) are held constant, rather than enforcing \(\sum X_j = 1\).

    Warning: this property is an experimental part of the Cantera API and may be changed or removed without notice.

  product_stoich_coeff(self, k_spec, int i_reaction)

    The stoichiometric coefficient of species `k_spec` as a product in reaction `i_reaction`.

  product_stoich_coeffs(self)

    The array of product stoichiometric coefficients. Element [k,i] of this array is the product stoichiometric coefficient of species k in reaction i.

    Deprecated since version 2.6: Behavior to change after Cantera 2.6; for new behavior, see property `Kinetics.reactant_stoich_coeffs3`.

  product_stoich_coeffs3

    The array of product stoichiometric coefficients. Element `[k,i]` of this array is the product stoichiometric coefficient of species `k` in reaction `i`.

    For sparse output, set `ct.use_sparse(True)`.

  product_stoich_coeffs_reversible

    The array of product stoichiometric coefficients of reversible reactions. Element `[k,i]` of this array is the product stoichiometric coefficient of species `k` in reaction `i`.

    For sparse output, set `ct.use_sparse(True)`.

  products(self, int i_reaction)

    The products portion of the reaction equation

    Deprecated since version 2.6: Replaced by property `Reaction.products`. Example: `gas.products(0)` is replaced by `gas.reaction(0).products`

  reactant_stoich_coeff(self, k_spec, int i_reaction)

    The stoichiometric coefficient of species `k_spec` as a reactant in reaction `i_reaction`.

  reactant_stoich_coeffs(self)

    The array of reactant stoichiometric coefficients. Element [k,i] of this array is the reactant stoichiometric coefficient of species k in reaction i.

    Deprecated since version 2.6: Behavior to change after Cantera 2.6; for new behavior, see property `Kinetics.reactant_stoich_coeffs3`.

  reactant_stoich_coeffs3

    The array of reactant stoichiometric coefficients. Element `[k,i]` of this array is the reactant stoichiometric coefficient of species `k` in reaction `i`.

    For sparse output, set `ct.use_sparse(True)`.

  reactants(self, int i_reaction)

    The reactants portion of the reaction equation

    Deprecated since version 2.6: Replaced by property `Reaction.reactants`. Example: `gas.reactants(0)` is replaced by `gas.reaction(0).reactants`

  reaction(self, int i_reaction)

    Return a `Reaction` object representing the reaction with index `i_reaction`. Changes to this object do not affect the `Kinetics` or `Solution` object until the `modify_reaction` function is called.

  reaction_equation(self, int i_reaction)

    The equation for the specified reaction. See also `reaction_equations`.

    Deprecated since version 2.6: Replaced by property `Reaction.equation`. Example: `gas.reaction_equation(0)` is replaced by `gas.reaction(0).equation`

  reaction_equations(self, indices=None)

    Returns a list containing the reaction equation for all reactions in the mechanism if `indices` is unspecified, or the equations for each reaction in the sequence `indices`. For example:

        >>> gas.reaction_equations()
        ['2 O + M <=> O2 + M', 'O + H + M <=> OH + M', 'O + H2 <=> H + OH', ...]
        >>> gas.reaction_equations([2,3])
        ['O + H + M <=> OH + M', 'O + H2 <=> H + OH']

    See also `reaction_equation`.

  reaction_phase_index

    The index of the phase where the reactions occur.

  reaction_type(self, int i_reaction)

    Type code of reaction `i_reaction`.

    Deprecated since version 2.6: Replaced by properties `Reaction.type` and `Reaction.rate.type`. Example: `gas.reaction_type(0)` is replaced by `gas.reaction(0).reaction_type` and `gas.reaction(0).rate.type`

  reactions(self)

    Return a list of all `Reaction` objects. Changes to these objects do not affect the `Kinetics` or `Solution` object until the `modify_reaction` function is called.

  reverse_rate_constants

    Reverse rate constants for all reactions. The computed values include all temperature-dependent, pressure-dependent, and third body contributions. Units are a combination of kmol, m^3 and s, that depend on the rate expression for the reaction.

    Deprecated since version 2.6: Behavior to change after Cantera 2.6; for Cantera 2.6, rate constants of three-body reactions are multiplied with third-body concentrations (no change to legacy behavior). After Cantera 2.6, results will no longer include third-body concentrations and be consistent with conventional definitions (see Eq. 9.75 in Kee, Coltrin and Glarborg, Chemically Reacting Flow, Wiley Interscience, 2003). To switch to new behavior, run `ct.use_legacy_rate_constants(False)`.

  reverse_rates_of_progress

    Reverse rates of progress for the reactions. [kmol/m^3/s] for bulk phases or [kmol/m^2/s] for surface phases.

  reverse_rates_of_progress_ddC

    Calculate derivatives for reverse rates-of-progress with respect to molar concentration at constant temperature, pressure and mole fractions.

    Warning: this property is an experimental part of the Cantera API and may be changed or removed without notice.

  reverse_rates_of_progress_ddP

    Calculate derivatives for reverse rates-of-progress with respect to pressure at constant temperature, molar concentration and mole fractions.

  reverse_rates_of_progress_ddT

    Calculate derivatives for reverse rates-of-progress with respect to temperature at constant pressure, molar concentration and mole fractions.

  reverse_rates_of_progress_ddX

    Calculate derivatives for reverse rates-of-progress with respect to species concentrations at constant temperature, pressure and molar concentration. For sparse output, set `ct.use_sparse(True)`.

    Note that for derivatives with respect to \(X_i\), all other \(X_j\) are held constant, rather than enforcing \(\sum X_j = 1\).

    Warning: this property is an experimental part of the Cantera API and may be changed or removed without notice.

  set_multiplier(self, double value, int i_reaction=-1)

    Set the multiplier for for reaction `i_reaction` to `value`. If `i_reaction` is not specified, then the multiplier for all reactions is set to `value`. See `multiplier`.

  third_body_concentrations

    Effective third-body concentrations used by individual reactions; values are only defined for reactions involving third-bodies and are set to not-a-number otherwise.

### InterfaceKinetics

class cantera.InterfaceKinetics(infile='', name='', adjacent=(), *args, **kwargs)

  Bases: `Kinetics`

  A kinetics manager for heterogeneous reaction mechanisms. The reactions are assumed to occur at an interface between bulk phases.

  advance_coverages(self, double dt, double rtol=1e-7, double atol=1e-14, double max_step_size=0, int max_steps=20000, int max_error_test_failures=7)

    This method carries out a time-accurate advancement of the surface coverages for a specified amount of time.

  advance_coverages_to_steady_state(self)

    This method advances the surface coverages to steady state.

  get_creation_rates(self, phase)

    Creation rates for each species in phase `phase`. Use the `creation_rates` property to get the creation rates for species in all phases.

  get_destruction_rates(self, phase)

    Destruction rates for each species in phase `phase`. Use the `destruction_rates` property to get the destruction rates for species in all phases.

  get_net_production_rates(self, phase)

    Net production rates for each species in phase `phase`. Use the `net_production_rates` property to get the net production rates for species in all phases.

  phase_index(self, phase)

    Get the index of the phase `phase`, where `phase` may specified using the phase object, the name, or the index itself.

  write_yaml(self, filename, phases=None, units=None, precision=None, skip_user_defined=None)

    See `_SolutionBase.write_yaml`.

## Reactions

These classes contain the definition of a single reaction, independent of a specific `Kinetics` object. For legacy objects (CTI/XML input), each class integrates associated rate expressions, whereas for the new, YAML-based implementation, reaction rate evaluation is handled by dedicated `ReactionRate` objects.

### Reaction

class cantera.Reaction(reactants=None, products=None, rate=None, equation=None, *, init=True, legacy=False, **kwargs)

  Bases: `object`

  A class which stores data about a reaction and its rate parameterization so that it can be added to a `Kinetics` object.

  Parameters

    - reactants – Value used to set `reactants`

    - products – Value used to set `products`

    - rate –

      The rate parameterization for the reaction, given as one of the following:

      > - a `ReactionRate` object

      > - a `dict` containing the parameters needed to construct a `ReactionRate` object, with keys corresponding to the YAML format

      > - a `dict` containing Arrhenius parameters (`A`, `b`, and `Ea`)

    - equation – The reaction equation, used to set the reactants and products if values for those arguments are not provided.

  Examples:

      R = ct.Reaction({"O": 1, "H2": 1}, {"H": 1, "OH": 1},
                      ct.ArrheniusRate(38.7, 2.7, 26191840.0))
      R = ct.Reaction(equation="O + H2 <=> H + OH",
                      rate={"A": 38.7, "b", 2.7, "Ea": 26191840.0})
      R = ct.Reaction(equation="HO2 <=> OH + O", rate=ChebyshevRate(...))

  The static methods `list_from_file`, `list_from_yaml`, `listFromCti`, and `listFromXml` can be used to create lists of `Reaction` objects from existing definitions in the YAML, CTI, or XML formats. All of the following will produce a list of the 325 reactions which make up the GRI 3.0 mechanism:

      R = ct.Reaction.list_from_file("gri30.yaml", gas)
      R = ct.Reaction.listFromCti(open("path/to/gri30.cti").read())
      R = ct.Reaction.listFromXml(open("path/to/gri30.xml").read())

  where `gas` is a `Solution` object with the appropriate thermodynamic model, which is the `ideal-gas` model in this case.

  The static method `list_from_yaml` can be used to create lists of `Reaction` objects from a YAML list:

      rxns = '''
        - equation: O + H2 <=> H + OH
          rate-constant: {A: 3.87e+04, b: 2.7, Ea: 6260.0}
        - equation: O + HO2 <=> OH + O2
          rate-constant: {A: 2.0e+13, b: 0.0, Ea: 0.0}
      '''
      R = ct.Reaction.list_from_yaml(rxns, gas)

  The methods `from_yaml`, `fromCti`, and `fromXml` can be used to create individual `Reaction` objects from definitions in these formats. In the case of using YAML or CTI definitions, it is important to verify that either the pre-exponential factor and activation energy are supplied in SI units, or that they have their units specified:

      R = ct.Reaction.from_yaml('''{equation: O + H2 <=> H + OH,
              rate-constant: {A: 3.87e+04 cm^3/mol/s, b: 2.7, Ea: 6260 cal/mol}}''',
              gas)

      R = ct.Reaction.fromCti('''reaction('O + H2 <=> H + OH',
              [3.87e1, 2.7, 2.619184e7])''')

      R = ct.Reaction.fromCti('''reaction('O + H2 <=> H + OH',
                      [(3.87e4, 'cm3/mol/s'), 2.7, (6260, 'cal/mol')])''')

  ID

    Get/Set the identification string for the reaction, which can be used in filtering operations.

  Pmax

    Maximum pressure [K] for the Chebyshev fit

    Deprecated since version 2.6: This property is for temporary backwards-compatibility with the deprecated `ChebyshevReaction` class. Replaced by `Reaction.rate.pressure_range[1]` for reactions where the rate is a a `ChebyshevRate`.

  Pmin

    Minimum pressure [Pa] for the Chebyshev fit

    Deprecated since version 2.6: This property is for temporary backwards-compatibility with the deprecated `ChebyshevReaction` class. Replaced by `Reaction.rate.pressure_range[0]` for reactions where the rate is a a `ChebyshevRate`.

  Tmax

    Maximum temperature [K] for the Chebyshev fit

    Deprecated since version 2.6: This property is for temporary backwards-compatibility with the deprecated `ChebyshevReaction` class. Replaced by `Reaction.rate.temperature_range[1]` for reactions where the rate is a `ChebyshevRate`.

  Tmin

    Minimum temperature [K] for the Chebyshev fit

    Deprecated since version 2.6: This property is for temporary backwards-compatibility with the deprecated `ChebyshevReaction` class. Replaced by `Reaction.rate.temperature_range[0]` for reactions where the rate is a `ChebyshevRate`.

  allow_negative_orders

    Get/Set a flag which is `True` if negative reaction orders are allowed. Default is `False`.

  allow_negative_pre_exponential_factor

    Get/Set whether the rate coefficient is allowed to have a negative pre-exponential factor.

    Deprecated since version 2.6: To be deprecated with version 2.6, and removed thereafter. Replaced by property `ArrheniusRateBase.allow_negative_pre_exponential_factor`.

  allow_nonreactant_orders

    Get/Set a flag which is `True` if reaction orders can be specified for non-reactant species. Default is `False`.

  clear_user_data(self)

    Clear all saved input data, so that the data given by `input_data` or `Solution.write_yaml` will only include values generated by Cantera based on the current object state.

  coeffs

    2D array of Chebyshev coefficients of size `(n_temperature, n_pressure)`.

    Deprecated since version 2.6: This property is for temporary backwards-compatibility with the deprecated `ChebyshevReaction` class. Replaced by `Reaction.rate.data` for reactions where the rate is a `ChebyshevRate`.

  coverage_deps

    Get/Set a dict containing adjustments to the Arrhenius rate expression dependent on surface species coverages. The keys of the dict are species names, and the values are tuples specifying the three coverage parameters `(a, m, E)` which are the modifiers for the pre-exponential factor [m, kmol, s units], the temperature exponent [nondimensional], and the activation energy [J/kmol], respectively.

    Deprecated since version 2.6: This property is for temporary backwards-compatibility with the deprecated `InterfaceReaction` class. Replaced by `Reaction.rate.coverage_dependencies` for reactions where the rate is a `InterfaceArrheniusRate` or `StickingArrheniusRate`.

  duplicate

    Get/Set a flag which is `True` if this reaction is marked as a duplicate or `False` otherwise.

  equation

    A string giving the chemical equation for this reaction. Determined automatically based on `reactants` and `products`.

  static fromCti(text)

    Create a Reaction object from its CTI string representation.

    Deprecated since version 2.5: The CTI input format is deprecated and will be removed in Cantera 3.0.

  static fromXml(text)

    Create a Reaction object from its XML string representation.

    Deprecated since version 2.5: The XML input format is deprecated and will be removed in Cantera 3.0.

  fromYaml(type cls, text, Kinetics kinetics=None)

    Create a `Reaction` object from its YAML string representation.

    Deprecated since version 2.6: To be deprecated with version 2.6, and removed thereafter. Replaced by `Reaction.from_yaml`.

  from_dict(type cls, data, Kinetics kinetics)

    Create a `Reaction` object from a dictionary corresponding to its YAML representation.

    An example for the creation of a Reaction from a dictionary is:

        rxn = Reaction.from_dict(
            {"equation": "O + H2 <=> H + OH",
             "rate-constant": {"A": 38.7, "b": 2.7, "Ea": 26191840.0}},
            kinetics=gas)

    In the example, `gas` is a Kinetics (or Solution) object.

    Parameters

      - data – A dictionary corresponding to the YAML representation.

      - kinetics – A `Kinetics` object whose associated phase(s) contain the species involved in the reaction.

  from_yaml(type cls, text, Kinetics kinetics)

    Create a `Reaction` object from its YAML string representation.

    An example for the creation of a Reaction from a YAML string is:

        rxn = Reaction.from_yaml('''
            equation: O + H2 <=> H + OH
            rate-constant: {A: 38.7, b: 2.7, Ea: 6260.0 cal/mol}
            ''', kinetics=gas)

    In the example, `gas` is a Kinetics (or Solution) object.

    Parameters

      - text – The YAML reaction string.

      - kinetics – A `Kinetics` object whose associated phase(s) contain the species involved in the reaction.

  input_data

    Get input data for this reaction with its current parameter values, along with any user-specified data provided with its input (YAML) definition.

  is_sticking_coefficient

    Get/Set a boolean indicating if the rate coefficient for this reaction is expressed as a sticking coefficient rather than the forward rate constant.

    Deprecated since version 2.6: This property is for temporary backwards-compatibility with the deprecated `InterfaceReaction` class. Replaced by dedicated rate objects `InterfaceArrheniusRate` and `StickingArrheniusRate`.

  static listFromCti(text)

    Create a list of `Reaction` objects from all the reactions defined in a CTI string.

    Deprecated since version 2.5: The CTI input format is deprecated and will be removed in Cantera 3.0.

  static listFromFile(filename, Kinetics kinetics=None, section=u'reactions')

    Create a list of Reaction objects from all of the reactions defined in a YAML, CTI, or XML file.

    For YAML input files, a `Kinetics` object is required as the second argument, and reactions from the section `section` will be returned.

    Directories on Cantera’s input file path will be searched for the specified file.

    In the case of an XML file, the `<reactions>` nodes are assumed to be children of the `<reactionsData>` node in a document with a `<ctml>` root node, as in the XML files produced by conversion from CTI files.

    Deprecated since version 2.5: The CTI and XML input formats are deprecated and will be removed in Cantera 3.0.

    Deprecated since version 2.6: To be removed after Cantera 2.6. Replaced by `Reaction.list_from_file`.

  static listFromXml(text)

    Create a list of Reaction objects from all the reaction defined in an XML string. The `<reaction>` nodes are assumed to be children of the `<reactionData>` node in a document with a `<ctml>` root node, as in the XML files produced by conversion from CTI files.

    Deprecated since version 2.5: The XML input format is deprecated and will be removed in Cantera 3.0.

  static listFromYaml(text, Kinetics kinetics)

    Create a list of `Reaction` objects from all the reactions defined in a YAML string.

    Deprecated since version 2.6: To be deprecated with version 2.6, and removed thereafter. Replaced by `Reaction.list_from_yaml`.

  static list_from_file(filename, Kinetics kinetics, section=u'reactions')

    Create a list of Reaction objects from all of the reactions defined in a YAML file. Reactions from the section `section` will be returned.

    Directories on Cantera’s input file path will be searched for the specified file.

  static list_from_yaml(text, Kinetics kinetics)

    Create a list of `Reaction` objects from all the reactions defined in a YAML string.

  nPressure

    Number of pressures over which the Chebyshev fit is computed

    Deprecated since version 2.6: This property is for temporary backwards-compatibility with the deprecated `ChebyshevReaction` class. Replaced by `Reaction.rate.n_pressure` for reactions where the rate is a a `ChebyshevRate`.

  nTemperature

    Number of temperatures over which the Chebyshev fit is computed

    Deprecated since version 2.6: This property is for temporary backwards-compatibility with the deprecated `ChebyshevReaction` class. Replaced by `Reaction.rate.n_temperature` for reactions where the rate is a `ChebyshevRate`.

  orders

    Get/Set the reaction order with respect to specific species as a dict with species names as the keys and orders as the values, or as a composition string. By default, mass-action kinetics is assumed, with the reaction order for each reactant species equal to each its stoichiometric coefficient.

  product_string

    A string representing the products side of the chemical equation for this reaction. Determined automatically based on `products`.

  products

    Get/Set the products in this reaction as a dict where the keys are species names and the values, are the stoichiometric coefficients, for example `{'CH3':1, 'H2O':1}`, or as a composition string, for example `'CH3:1, H2O:1'`.

  rate

    Get/Set the `ArrheniusRate` rate coefficient for this reaction.

  rate_coeff_units

    Get reaction rate coefficient units

  rates

    For reactions with Plog rates, get/set the rate coefficients for this reaction as a list of (pressure, rate) tuples.

    Deprecated since version 2.6: This property is for temporary backwards-compatibility with the deprecated `PlogReaction` class. Replaced by `Reaction.rate.rates` for reactions where the rate is a `PlogRate`.

  reactant_string

    A string representing the reactants side of the chemical equation for this reaction. Determined automatically based on `reactants`.

  reactants

    Get/Set the reactants in this reaction as a dict where the keys are species names and the values, are the stoichiometric coefficients, for example `{'CH4':1, 'OH':1}`, or as a composition string, for example `'CH4:1, OH:1'`.

  reaction_type

    Retrieve the native type name of the reaction.

  reversible

    Get/Set a flag which is `True` if this reaction is reversible or `False` otherwise.

  set_parameters(self, Tmin, Tmax, Pmin, Pmax, coeffs)

    For Chebyshev reactions, simultaneously set values for `Tmin`, `Tmax`, `Pmin`, `Pmax`, and `coeffs`.

    Deprecated since version 2.6: This property is for temporary backwards-compatibility with the deprecated `ChebyshevReaction` class. Replaced by `ChebyshevRate` constructor for reactions where the rate is a `ChebyshevRate`.

  sticking_species

    The name of the sticking species. Needed only for reactions with multiple non-surface reactant species, where the sticking species is ambiguous.

    Deprecated since version 2.6: To be deprecated with version 2.6, and removed thereafter. Replaced by property `StickingArrheniusRate.sticking_species`.

  update_user_data(self, data)

    Add the contents of the provided `dict` as additional fields when generating YAML phase definition files with `Solution.write_yaml` or in the data returned by `input_data`. Existing keys with matching names are overwritten.

  use_motz_wise_correction

    Get/Set a boolean indicating whether to use the correction factor developed by Motz & Wise for reactions with high (near-unity) sticking coefficients when converting the sticking coefficient to a rate coefficient.

    Deprecated since version 2.6: This property is for temporary backwards-compatibility with the deprecated `InterfaceReaction` class. Replaced by `Reaction.rate.motz_wise_correction` for reactions where the rate is a `StickingArrheniusRate`.

  uses_legacy

    Indicate whether reaction uses a legacy implementation

### ElementaryReaction

class cantera.ElementaryReaction(reactants=None, products=None, rate=None, equation=None, *, Kinetics kinetics=None, init=True, **kwargs)

  Bases: `Reaction`

  A reaction which follows mass-action kinetics with a modified Arrhenius reaction rate.

  An example for the definition of an `ElementaryReaction` object is given as:

      rxn = ElementaryReaction(
          equation="O + H2 <=> H + OH",
          rate={"A": 38.7, "b": 2.7, "Ea": 2.619184e+07},
          kinetics=gas)

  The YAML description corresponding to this reaction is:

      equation: O + H2 <=> H + OH
      rate-constant: {A: 3.87e+04 cm^3/mol/s, b: 2.7, Ea: 6260.0 cal/mol}

  Deprecated since version 2.6: To be removed after Cantera 2.6. Capabilities merged directly into the base `Reaction` class.

  allow_negative_pre_exponential_factor

    Get/Set whether the rate coefficient is allowed to have a negative pre-exponential factor.

    Deprecated since version 2.6: To be deprecated with version 2.6, and removed thereafter. Replaced by property `ArrheniusRateBase.allow_negative_pre_exponential_factor`.

  rate

    Get/Set the `ArrheniusRate` rate coefficient for this reaction.

### ThreeBodyReaction

class cantera.ThreeBodyReaction(reactants=None, products=None, rate=None, equation=None, *, efficiencies=None, Kinetics kinetics=None, legacy=False, init=True, **kwargs)

  Bases: `ElementaryReaction`

  A reaction with a non-reacting third body “M” that acts to add or remove energy from the reacting species.

  An example for the definition of an `ThreeBodyReaction` object is given as:

      rxn = ThreeBodyReaction(
          equation="2 O + M <=> O2 + M",
          rate={"A": 1.2e+17, "b": -1.0, "Ea": 0.0},
          efficiencies={"H2": 2.4, "H2O": 15.4, "AR": 0.83},
          kinetics=gas)

  The YAML description corresponding to this reaction is:

      equation: 2 O + M <=> O2 + M
      type: three-body
      rate-constant: {A: 1.2e+17 cm^6/mol^2/s, b: -1.0, Ea: 0.0 cal/mol}
      efficiencies: {H2: 2.4, H2O: 15.4, AR: 0.83}

  default_efficiency

    Get/Set the default third-body efficiency for this reaction, used for species used for species not in `efficiencies`.

  efficiencies

    Get/Set a `dict` defining non-default third-body efficiencies for this reaction, where the keys are the species names and the values are the efficiencies.

  efficiency(self, species)

    Get the efficiency of the third body named `species` considering both the default efficiency and species-specific efficiencies.

### FalloffReaction

class cantera.FalloffReaction(reactants=None, products=None, rate=None, equation=None, *, efficiencies=None, Kinetics kinetics=None, init=True, legacy=False, **kwargs)

  Bases: `Reaction`

  A reaction that is first-order in [M] at low pressure, like a third-body reaction, but zeroth-order in [M] as pressure increases.

  An example for the definition of a `FalloffReaction` object is given as:

      rxn = FalloffReaction(
          equation="2 OH (+ M) <=> H2O2 (+ M)",
          rate=ct.TroeRate(low=ct.Arrhenius(2.3e+12, -0.9, -7112800.0),
                           high=ct.Arrhenius(7.4e+10, -0.37, 0),
                           falloff_coeffs=[0.7346, 94.0, 1756.0, 5182.0]),
          efficiencies={"AR": 0.7, "H2": 2.0, "H2O": 6.0},
          kinetics=gas)

  The YAML description corresponding to this reaction is:

      equation: 2 OH (+ M) <=> H2O2 (+ M)  # Reaction 3
      type: falloff
      low-P-rate-constant: {A: 2.3e+12, b: -0.9, Ea: -1700.0 cal/mol}
      high-P-rate-constant: {A: 7.4e+10, b: -0.37, Ea: 0.0 cal/mol}
      Troe: {A: 0.7346, T3: 94.0, T1: 1756.0, T2: 5182.0}
      efficiencies: {AR: 0.7, H2: 2.0, H2O: 6.0}

  allow_negative_pre_exponential_factor

    Get/Set whether the rate coefficient is allowed to have a negative pre-exponential factor.

    Deprecated since version 2.6: To be deprecated with version 2.6, and removed thereafter. Replaced by property `FalloffRate.allow_negative_pre_exponential_factor`.

  default_efficiency

    Get/Set the default third-body efficiency for this reaction, used for species used for species not in `efficiencies`.

  efficiencies

    Get/Set a `dict` defining non-default third-body efficiencies for this reaction, where the keys are the species names and the values are the efficiencies.

  efficiency(self, species)

    Get the efficiency of the third body named `species` considering both the default efficiency and species-specific efficiencies.

  falloff

    Get/Set the `Falloff` function used to blend the high- and low-pressure rate coefficients

  high_rate

    Get/Set the `Arrhenius` rate constant in the high-pressure limit

  low_rate

    Get/Set the `Arrhenius` rate constant in the low-pressure limit

  rate

    Get/Set the `FalloffRate` rate coefficients for this reaction.

### ChemicallyActivatedReaction

class cantera.ChemicallyActivatedReaction

  Bases: `FalloffReaction`

  A reaction where the rate decreases as pressure increases due to collisional stabilization of a reaction intermediate. Like a `FalloffReaction`, except that the forward rate constant is written as being proportional to the low- pressure rate constant.

### PlogReaction

class cantera.PlogReaction(reactants=None, products=None, rate=None, equation=None, *, Kinetics kinetics=None, init=True, **kwargs)

  Bases: `Reaction`

  A pressure-dependent reaction parameterized by logarithmically interpolating between Arrhenius rate expressions at various pressures.

  An example for the definition of a `PlogReaction` object is given as:

      rxn = PlogReaction(
          equation="H2 + O2 <=> 2 OH",
          rate=[(1013.25, Arrhenius(1.2124e+16, -0.5779, 45491376.8)),
                (101325., Arrhenius(4.9108e+31, -4.8507, 103649395.2)),
                (1013250., Arrhenius(1.2866e+47, -9.0246, 166508556.0)),
                (10132500., Arrhenius(5.9632e+56, -11.529, 220076726.4))],
          kinetics=gas)

  The YAML description corresponding to this reaction is:

      equation: H2 + O2 <=> 2 OH
      type: pressure-dependent-Arrhenius
      rate-constants:
      - {P: 0.01 atm, A: 1.2124e+16, b: -0.5779, Ea: 1.08727e+04 cal/mol}
      - {P: 1.0 atm, A: 4.9108e+31, b: -4.8507, Ea: 2.47728e+04 cal/mol}
      - {P: 10.0 atm, A: 1.2866e+47, b: -9.0246, Ea: 3.97965e+04 cal/mol}
      - {P: 100.0 atm, A: 5.9632e+56, b: -11.529, Ea: 5.25996e+04 cal/mol}or.

  Deprecated since version 2.6: To be deprecated with version 2.6, and removed thereafter. Implemented by the `Reaction` class with a `PlogRate` reaction rate.

  rates

    Get/Set the rate coefficients for this reaction, which are given as a list of (pressure, `Arrhenius`) tuples.

### ChebyshevReaction

class cantera.ChebyshevReaction(reactants=None, products=None, rate=None, equation=None, *, Kinetics kinetics=None, init=True, **kwargs)

  Bases: `Reaction`

  A pressure-dependent reaction parameterized by a bivariate Chebyshev polynomial in temperature and pressure.

  An example for the definition of a `ChebyshevReaction` object is given as:

      rxn = ChebyshevReaction(
          equation="HO2 <=> OH + O",
          rate={"temperature-range": [290.0, 3000.0],
                "pressure-range": [1e3, 1e8],
                "data": [[8.2883, -1.1397, -0.12059, 0.016034],
                         [1.9764, 1.0037, 7.2865e-03, -0.030432],
                         [0.3177, 0.26889, 0.094806, -7.6385e-03]]},
          kinetics=gas)

  The YAML description corresponding to this reaction is:

      equation: HO2 <=> OH + O
      type: Chebyshev
      temperature-range: [290.0, 3000.0]
      pressure-range: [1.e-03 bar, 10. bar]
      data:
      - [8.2883, -1.1397, -0.12059, 0.016034]
      - [1.9764, 1.0037, 7.2865e-03, -0.030432]
      - [0.3177, 0.26889, 0.094806, -7.6385e-03]

  Deprecated since version 2.6: To be deprecated with version 2.6, and removed thereafter. Implemented by the `Reaction` class with a `ChebyshevRate` reaction rate.

  Pmax

    Maximum pressure [Pa] for the Chebyshev fit

    Deprecated since version 2.6: To be deprecated with version 2.6, and removed thereafter. Replaced by property `ChebyshevRate.pressure_range[1]`.

  Pmin

    Minimum pressure [Pa] for the Chebyshev fit

    Deprecated since version 2.6: To be deprecated with version 2.6, and removed thereafter. Replaced by property `ChebyshevRate.pressure_range[0]`.

  Tmax

    Maximum temperature [K] for the Chebyshev fit

    Deprecated since version 2.6: To be deprecated with version 2.6, and removed thereafter. Replaced by property `ChebyshevRate.temperature_range[1]`.

  Tmin

    Minimum temperature [K] for the Chebyshev fit

    Deprecated since version 2.6: To be deprecated with version 2.6, and removed thereafter. Replaced by property `ChebyshevRate.temperature_range[0]`.

  coeffs

    2D array of Chebyshev coefficients of size `(n_temperature, n_pressure)`.

    Deprecated since version 2.6: To be deprecated with version 2.6, and removed thereafter. Replaced by property `ChebyshevRate.data`.

  nPressure

    Number of pressures over which the Chebyshev fit is computed

    Deprecated since version 2.6: To be deprecated with version 2.6, and removed thereafter. Replaced by property `ChebyshevRate.n_pressure`.

  nTemperature

    Number of temperatures over which the Chebyshev fit is computed

    Deprecated since version 2.6: To be deprecated with version 2.6, and removed thereafter. Replaced by property `ChebyshevRate.n_temperature`.

  set_parameters(self, Tmin, Tmax, Pmin, Pmax, coeffs)

    Simultaneously set values for `Tmin`, `Tmax`, `Pmin`, `Pmax`, and `coeffs`.

    Deprecated since version 2.6: To be deprecated with version 2.6, and removed thereafter. Replaced by `ChebyshevRate` constructor.

### InterfaceReaction

class cantera.InterfaceReaction(equation=None, rate=None, Kinetics kinetics=None, init=True, legacy=False, **kwargs)

  Bases: `ElementaryReaction`

  A reaction occurring on an `Interface` (that is, a surface or an edge)

  > rxn = InterfaceReaction(

  >   equation=”H(S) + O(S) <=> OH(S) + PT(S)”, rate={“A”: 3.7e+20, “b”: 0, “Ea”: 1.15e7}, kinetics=surf)

  The YAML description corresponding to this reaction is:

      equation: H(S) + O(S) <=> OH(S) + PT(S)
      rate-constant: {A: 3.7e+20, b: 0, Ea: 11500 J/mol}

  Deprecated since version 2.6: To be deprecated with version 2.6, and removed thereafter. Implemented by the `Reaction` class with either `InterfaceArrheniusRate` or `StickingArrheniusRate` reaction rate.

  coverage_deps

    Get/Set a dict containing adjustments to the Arrhenius rate expression dependent on surface species coverages. The keys of the dict are species names, and the values are tuples specifying the three coverage parameters `(a, m, E)` which are the modifiers for the pre-exponential factor [m, kmol, s units], the temperature exponent [nondimensional], and the activation energy [J/kmol], respectively.

    Deprecated since version 2.6: To be deprecated with version 2.6, and removed thereafter. Replaced by property `InterfaceRateBase.coverage_dependencies`.

  is_sticking_coefficient

    Get/Set a boolean indicating if the rate coefficient for this reaction is expressed as a sticking coefficient rather than the forward rate constant.

    Deprecated since version 2.6: To be deprecated with version 2.6, and removed thereafter. Replaced by dedicated classes `StickRateBase`.

  sticking_species

    The name of the sticking species. Needed only for reactions with multiple non-surface reactant species, where the sticking species is ambiguous.

    Deprecated since version 2.6: To be deprecated with version 2.6, and removed thereafter. Replaced by property `stickRateBase.sticking_species`.

  use_motz_wise_correction

    Get/Set a boolean indicating whether to use the correction factor developed by Motz & Wise for reactions with high (near-unity) sticking coefficients when converting the sticking coefficient to a rate coefficient.

    Deprecated since version 2.6: To be deprecated with version 2.6, and removed thereafter. Replaced by property `stickRateBase.mote_wise_correction`.

## Reaction Rates

### ReactionRate

class cantera.ReactionRate

  Bases: `object`

  Base class for ReactionRate objects.

  ReactionRate objects are used to calculate reaction rates and are associated with a Reaction object.

  from_dict(type cls, data)

    Create a `ReactionRate` object from a dictionary corresponding to its YAML representation.

    An example for the creation of a `ReactionRate` from a dictionary is:

        rate = ReactionRate.from_dict(
            {"rate-constant": {"A": 38.7, "b": 2.7, "Ea": 26191840.0}})

    Parameters

      data – A dictionary corresponding to the YAML representation.

  from_yaml(type cls, text)

    Create a `ReactionRate` object from its YAML string representation.

    An example for the creation of a `ReactionRate` from a YAML string is:

        rate = ReactionRate.from_yaml(
            "rate-constant: {A: 38.7, b: 2.7, Ea: 6260.0 cal/mol}")

    Units for `A` require a unit system with length in `m` and quantity in `kmol` (standard Cantera units).

    Parameters

      text – The YAML reaction rate string.

  input_data

    Get input data for this reaction rate with its current parameter values.

  type

    Get the C++ ReactionRate type

### ArrheniusRateBase

class cantera.ArrheniusRateBase(input_data)

  Bases: `ReactionRate`

  Base class collecting commonly used features of Arrhenius-type rate objects. Objects should be instantiated by specialized classes, for example `ArrheniusRate`, `BlowersMaselRate` and `TwoTempPlasmaRate`.

  activation_energy

    The activation energy `E` [J/kmol].

  allow_negative_pre_exponential_factor

    Get/Set whether the rate coefficient is allowed to have a negative pre-exponential factor.

  pre_exponential_factor

    The pre-exponential factor `A` in units of m, kmol, and s raised to powers depending on the reaction order.

  temperature_exponent

    The temperature exponent `b`.

### ArrheniusRate

class cantera.ArrheniusRate(A, b, Ea)

  Bases: `ArrheniusRateBase`

  A reaction rate coefficient which depends on temperature only and follows the modified Arrhenius form:

  \[k_f = A T^b \exp(-\tfrac{E_a}{RT})\]

  where `A` is the `pre_exponential_factor`, `b` is the `temperature_exponent`, and `Ea` is the `activation_energy`.

### BlowersMaselRate

class cantera.BlowersMaselRate(A, b, Ea, w)

  Bases: `ArrheniusRateBase`

  A reaction rate coefficient which depends on temperature and enthalpy change of the reaction follows the Blowers-Masel approximation and modified Arrhenius form described in `ArrheniusRate`.

  bond_energy

    Average bond dissociation energy of the bond being formed and broken in the reaction `E` [J/kmol].

  delta_enthalpy

    Enthalpy change of reaction `deltaH` [J/kmol]

    The enthalpy change of reaction is a function of temperature and thus not an independent property. Accordingly, the setter should be only used for testing purposes, as any value will be overwritten by an update of the thermodynamic state.

    Warning: this property is an experimental part of the Cantera API and may be changed or removed without notice.

### TwoTempPlasmaRate

class cantera.TwoTempPlasmaRate(A, b, Ea_gas, Ea_electron)

  Bases: `ArrheniusRateBase`

  A reaction rate coefficient which depends on both gas and electron temperature with the form similar to the modified Arrhenius form. Specifically, the temperature exponent (b) is applied to the electron temperature instead. In addition, the exponential term with activation energy for electron is included.

  \[k_f = A T_e^b \exp(-\tfrac{E_{a,g}}{RT}) \exp(\tfrac{E_{a,e}(T_e - T)}{R T T_e})\]

  where \(A\) is the `pre_exponential_factor`, \(b\) is the `temperature_exponent`, \(E_{a,g}\) (`Ea_gas`) is the `activation_energy`, and \(E_{a,e}\) (`Ea_electron`) is the `activation_electron_energy`.

  activation_electron_energy

    The activation electron energy \(E_{a,e}\) [J/kmol].

### FalloffRate

class cantera.FalloffRate

  Bases: `ReactionRate`

  Base class for parameterizations used to describe the fall-off in reaction rates due to intermolecular energy transfer. These objects are used by `FalloffReaction`. Note that `FalloffRate` is a base class for specialized fall-off parameterizations and cannot be instantiated by itself.

  allow_negative_pre_exponential_factor

    Get/Set whether the rate coefficient is allowed to have a negative pre-exponential factor.

  chemically_activated

    Get whether the object is a chemically-activated reaction rate.

  falloff_coeffs

    The array of coefficients used to define this falloff function.

  falloff_function(self, double temperature, double conc3b)

    Evaluate the falloff function based on temperature and third-body concentration.

  high_rate

    Get/Set the `Arrhenius` rate constant in the high-pressure limit

  low_rate

    Get/Set the `Arrhenius` rate constant in the low-pressure limit

### LindemannRate

class cantera.LindemannRate(low, high, falloff_coeffs)

  Bases: `FalloffRate`

  The Lindemann falloff parameterization.

  This class implements the simple falloff function \(F(T,P_r) = 1.0\).

### TroeRate

class cantera.TroeRate(low, high, falloff_coeffs)

  Bases: `FalloffRate`

  The 3- or 4-parameter Troe falloff function.

  Parameters

    falloff_coeffs – An array of 3 or 4 parameters: \([a, T^{***}, T^*, T^{**}]\) where the final parameter is optional (with a default value of 0).

### SriRate

class cantera.SriRate(low, high, falloff_coeffs)

  Bases: `FalloffRate`

  The 3- or 5-parameter SRI falloff function.

  Parameters

    falloff_coeffs – An array of 3 or 5 parameters: \([a, b, c, d, e]\) where the last two parameters are optional (with default values of 1 and 0, respectively).

### TsangRate

class cantera.TsangRate(low, high, falloff_coeffs)

  Bases: `FalloffRate`

  The Tsang falloff parameterization.

### PlogRate

class cantera.PlogRate(rates)

  Bases: `ReactionRate`

  A pressure-dependent reaction rate parameterized by logarithmically interpolating between Arrhenius rate expressions at various pressures.

  rates

    Get/Set the rate coefficients for this reaction, which are given as a list of (pressure, `Arrhenius`) tuples.

### ChebyshevRate

class cantera.ChebyshevRate(temperature_range, pressure_range, data)

  Bases: `ReactionRate`

  A pressure-dependent reaction rate parameterized by a bivariate Chebyshev polynomial in temperature and pressure.

  data

    2D array of Chebyshev coefficients where rows and columns correspond to temperature and pressure dimensions over which the Chebyshev fit is computed.

  n_pressure

    Number of pressures over which the Chebyshev fit is computed (same as number of columns of `data` property).

  n_temperature

    Number of temperatures over which the Chebyshev fit is computed. (same as number of rows of `data` property).

  pressure_range

    Valid pressure range [Pa] for the Chebyshev fit

  temperature_range

    Valid temperature range [K] for the Chebyshev fit

### CustomRate

class cantera.CustomRate(k)

  Bases: `ReactionRate`

  A custom rate coefficient which depends on temperature only.

  The simplest way to create a `CustomRate` object is to use a lambda function, for example:

      rr = CustomRate(lambda T: 38.7 * T**2.7 * exp(-3150.15/T))

  Warning: this class is an experimental part of the Cantera API and may be changed or removed without notice.

  set_rate_function(self, k)

    Set the function describing a custom reaction rate:

        rr = CustomRate()
        rr.set_rate_function(lambda T: 38.7 * T**2.7 * exp(-3150.15/T))

### InterfaceRateBase

class cantera.InterfaceRateBase

  Bases: `ArrheniusRateBase`

  Base class collecting commonly used features of Arrhenius-type rate objects that include coverage dependencies.

  beta

    Return the charge transfer beta parameter

  coverage_dependencies

    Get/set a dictionary containing adjustments to the Arrhenius rate expression dependent on surface species coverages. The keys of the dictionary are species names, and the values are dictionaries specifying the three coverage parameters `a`, `m` and `E` which are the modifiers for the pre-exponential factor [m, kmol, s units], the temperature exponent [nondimensional], and the activation energy [J/kmol], respectively.

  set_species(self, species)

    Set association with an ordered list of all species associated with an `InterfaceKinetics` object.

  site_density

    Site density [kmol/m^2]

    The site density is not an independent property, as it is set by an associated `InterfaceKinetics` object. Accordingly, the setter should be only used for testing purposes, as the value will be overwritten by an update of the thermodynamic state.

    Warning: this property is an experimental part of the Cantera API and may be changed or removed without notice.

  uses_electrochemistry

    Return boolean flag indicating whether rate involves a charge transfer.

### InterfaceArrheniusRate

class cantera.InterfaceArrheniusRate(A, b, Ea)

  Bases: `InterfaceRateBase`

  A reaction rate coefficient which depends on temperature and interface coverage

### InterfaceBlowersMaselRate

class cantera.InterfaceBlowersMaselRate(A, b, Ea0, w)

  Bases: `InterfaceRateBase`

  A reaction rate coefficient which depends on temperature and enthalpy change of the reaction follows the Blowers-Masel approximation and modified Arrhenius form described in `ArrheniusRate`.

  bond_energy

    Average bond dissociation energy of the bond being formed and broken in the reaction `E` [J/kmol].

  delta_enthalpy

    Enthalpy change of reaction `deltaH` [J/kmol]

    The enthalpy change of reaction is a function of temperature and thus not an independent property. Accordingly, the setter should be only used for testing purposes, as any value will be overwritten by an update of the thermodynamic state.

    Warning: this property is an experimental part of the Cantera API and may be changed or removed without notice.

### StickRateBase

class cantera.StickRateBase

  Bases: `InterfaceRateBase`

  Base class collecting commonly used features of Arrhenius-type sticking rate objects that include coverage dependencies.

  motz_wise_correction

    Get/Set a boolean indicating whether to use the correction factor developed by Motz & Wise for reactions with high (near-unity) sticking coefficients when converting the sticking coefficient to a rate coefficient.

  sticking_order

    The exponent applied to site density (sticking order).

    The sticking order is not an independent property and is detected automatically by Cantera. Accordingly, the setter should be only used for testing purposes.

    Warning: this property is an experimental part of the Cantera API and may be changed or removed without notice.

  sticking_species

    The name of the sticking species. Needed only for reactions with multiple non-surface reactant species, where the sticking species is ambiguous.

  sticking_weight

    The molecular weight of the sticking species.

    The sticking weight is not an independent property and is detected automatically by Cantera. Accordingly, the setter should be only used for testing purposes.

    Warning: this property is an experimental part of the Cantera API and may be changed or removed without notice.

### StickingArrheniusRate

class cantera.StickingArrheniusRate(A, b, Ea)

  Bases: `StickRateBase`

  A surface sticking rate expression based on the Arrhenius parameterization

### StickingBlowersMaselRate

class cantera.StickingBlowersMaselRate(A, b, Ea0, w)

  Bases: `StickRateBase`

  A surface sticking rate expression based on the Blowers-Masel parameterization

  bond_energy

    Average bond dissociation energy of the bond being formed and broken in the reaction `E` [J/kmol].

  delta_enthalpy

    Enthalpy change of reaction `deltaH` [J/kmol]

    The enthalpy change of reaction is a function of temperature and thus not an independent property. Accordingly, the setter should be only used for testing purposes, as any value will be overwritten by an update of the thermodynamic state.

    Warning: this property is an experimental part of the Cantera API and may be changed or removed without notice.

## Auxiliary Reaction Data (legacy only)

### Arrhenius

class cantera.Arrhenius(A, b, E)

  Bases: `object`

  A reaction rate coefficient which depends on temperature only and follows the modified Arrhenius form:

  \[k_f = A T^b \exp(-\tfrac{E}{RT})\]

  where `A` is the `pre_exponential_factor`, `b` is the `temperature_exponent`, and `E` is the `activation_energy`.

  activation_energy

    The activation energy `E` [J/kmol].

  pre_exponential_factor

    The pre-exponential factor `A` in units of m, kmol, and s raised to powers depending on the reaction order.

  temperature_exponent

    The temperature exponent `b`.

### Falloff

class cantera.Falloff(params=(), init=True)

  Bases: `object`

  A parameterization used to describe the fall-off in reaction rate constants due to intermolecular energy transfer. These functions are used by reactions defined using the `FalloffReaction` and `ChemicallyActivatedReaction` classes.

  This base class implements the simple falloff function \(F(T,P_r) = 1.0\).

  Parameters

    - params – Not used for the “simple” falloff parameterization.

    - init – Used internally when wrapping FalloffRate objects returned from C++.

  Deprecated since version 2.6: To be removed after Cantera 2.6. Capabilities merged into the `LindemannRate` class.

  parameters

    The array of parameters used to define this falloff function.

  type

    A string defining the type of the falloff parameterization

### TroeFalloff

class cantera.TroeFalloff(params=(), init=True)

  Bases: `Falloff`

  The 3- or 4-parameter Troe falloff function.

  Parameters

    params – An array of 3 or 4 parameters: \([a, T^{***}, T^*, T^{**}]\) where the final parameter is optional (with a default value of 0).

  Deprecated since version 2.6: To be removed after Cantera 2.6. Capabilities merged into the `TroeRate` class.

### SriFalloff

class cantera.SriFalloff(params=(), init=True)

  Bases: `Falloff`

  The 3- or 5-parameter SRI falloff function.

  Parameters

    params – An array of 3 or 5 parameters: \([a, b, c, d, e]\) where the last two parameters are optional (with default values of 1 and 0, respectively).

  Deprecated since version 2.6: To be removed after Cantera 2.6. Capabilities merged into the `SriRate` class.

## Reaction Path Analysis

### ReactionPathDiagram

class cantera.ReactionPathDiagram(Kinetics kin, str element)

  Bases: `object`

  ReactionPathDiagram(Kinetics kin, unicode element)

  Create a reaction path diagram for the fluxes of the element `element` according the the net reaction rates determined by the `Kinetics` object `kin`.

  add(self, ReactionPathDiagram other)

    Add fluxes from `other` to this diagram

  arrow_width

    Get/Set the arrow width. If < 0, then scale with flux value.

  bold_color

    Get/Set the color for bold lines

  bold_threshold

    Get/Set the minimum relative flux for bold lines

  build(self, verbose=False)

    Build the reaction path diagram. Called automatically by methods which return representations of the diagram, for example write_dot().

  dashed_color

    Get/Set the color for dashed lines

  display_only(self, int k)

    Include only species and fluxes that are directly connected to the species with index `k`. Set to -1 to include all species.

  dot_options

    Get/Set options for the ‘dot’ program

  flow_type

    Get/Set the way flows are drawn. Either ‘NetFlow’ or ‘OneWayFlow’

  font

    Get/Set the name of the font used

  get_data(self)

    Get a (roughly) human-readable representation of the reaction path diagram.

  get_dot(self)

    Return a string containing the reaction path diagram formatted for use by Graphviz’s ‘dot’ program.

  label_threshold

    Get/Set the minimum relative flux for labels

  log

    Logging messages generated while building the reaction path diagram

  normal_color

    Get/Set the color for normal-weight lines

  normal_threshold

    Get/Set the maximum relative flux for dashed lines

  scale

    Get/Set the scaling factor for the fluxes. Set to -1 to normalize by the maximum net flux.

  show_details

    Get/Set whether to show the details of which reactions contribute to the flux.

  threshold

    Get/Set the threshold for the minimum flux relative value that will be plotted.

  title

    Get/Set the diagram title

  write_dot(self, filename)

    Write the reaction path diagram formatted for use by Graphviz’s ‘dot’ program to the file named `filename`.