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ReStructuredText
323 lines
9.9 KiB
ReStructuredText
.. highlight:: yaml
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.. _sec-yaml-reactions:
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*********
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Reactions
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*********
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The fields common to all ``reaction`` entries are:
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``equation``
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The stoichiometric equation for the reaction. Each term (i.e.,
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stoichiometric coefficient, species name, ``+`` or ``<=>``) in the equation
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must be separated by a space.
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Reversible reactions may be written using ``<=>`` or ``=`` to separate
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reactants and products. Irreversible reacions are written using ``=>``.
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``type``
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A string specifying the type of reaction or rate coefficient
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parameterization. The default is ``elementary``. Reaction types are:
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- :ref:`elementary <sec-elementary>`
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- :ref:`three-body <sec-three-body>`
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- :ref:`falloff <sec-falloff>`
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- :ref:`chemically-activated <sec-chemically-activated>`
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- :ref:`pressure-dependent-Arrhenius <sec-pressure-dependent-Arrhenius>`
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- :ref:`Chebyshev <sec-Chebyshev>`
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Reactions on surfaces or edges are automatically treated as
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:ref:`interface <sec-interface-reaction>` reactions, and reactions that
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involve charge transfer between phases are automatically treated as
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:ref:`electrochemical <sec-electrochemical-reaction>` reactions, without the
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need to specify the ``type``.
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``duplicate``
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Boolean indicating whether the reaction is a known duplicate of another
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reaction. The default is ``false``.
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``orders``
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An optional mapping of species to explicit reaction orders to use. Reaction
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orders for reactant species not explicitly mentioned are taken to be their
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respective stoichiometric coefficients. See
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`Reaction orders <https://cantera.org/science/reactions.html#reaction-orders>`__
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for additional information.
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``negative-orders``
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Boolean indicating whether negative reaction orders are allowed. The
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default is ``false``.
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``nonreactant-orders``
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Boolean indicating whether orders for non-reactant species are allowed.
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The default is ``false``.
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Depending on the reaction ``type``, other fields may be necessary to specify
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the rate of the reaction.
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.. _sec-arrhenius:
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Arrhenius expression
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====================
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Arrhenius expressions can be specified as either a three-element list containing
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the pre-exponential factor :math:`A`, the temperature exponent :math:`b`, and
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the activation energy :math:`E_a`, or a mapping containing the fields ``A``,
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``b``, and ``Ea``. The following are equivalent::
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{A: -2.70000E+13 cm^3/mol/s, b: 0, Ea: 355 cal/mol}
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[-2.70000E+13 cm^3/mol/s, 0, 355 cal/mol]
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.. _sec-efficiencies:
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Efficiencies
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============
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Some reaction types include parameters for the "efficiency" of different species
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as third-body colliders. For these reactions, the following additional fields
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are supported:
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``efficiencies``
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A mapping of species names to efficiency values
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``default-efficiency``
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The efficiency for use for species not included in the ``efficiencies``
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mapping. Defaults to 1.0.
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Reaction types
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==============
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.. _sec-elementary:
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``elementary``
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--------------
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A homogeneous reaction with a pressure-independent rate coefficient and mass
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action kinetics, as
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`described here <https://cantera.org/science/reactions.html#reactions-with-a-pressure-independent-rate>`__.
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Additional fields are:
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``rate-constant``
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An :ref:`Arrhenius-type <sec-arrhenius>` list or mapping.
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``negative-A``
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A boolean indicating whether a negative value for the pre-exponential factor
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is allowed. The default is ``false``.
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Example::
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equation: N + NO <=> N2 + O
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rate-constant: {A: -2.70000E+13 cm^3/mol/s, b: 0, Ea: 355 cal/mol}
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negative-A: true
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.. _sec-three-body:
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``three-body``
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--------------
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A three body reaction as
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`described here <https://cantera.org/science/reactions.html#three-body-reactions>`__.
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The reaction equation should include the third body collision partner ``M``.
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Includes the fields of an ``elementary`` reaction, plus the fields for
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specifying :ref:`efficiencies <sec-efficiencies>`.
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Example::
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equation: 2 O + M = O2 + M
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type: three-body
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rate-constant: [1.20000E+17 cm^6/mol^2/s, -1, 0]
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efficiencies: {AR: 0.83, H2O: 5}
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.. _sec-falloff:
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``falloff``
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-----------
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A falloff reaction as
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`described here <https://cantera.org/science/reactions.html#falloff-reactions>`__.
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The reaction equation should include the pressure-dependent third body collision
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partner ``(+M)`` or ``(+name)`` where ``name`` is the name of a species. The
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latter case is equivalent to setting the efficiency for ``name`` to 1 and the
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efficiency for all other species to 0.
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Includes field for specifying :ref:`efficiencies <sec-efficiencies>` as well
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as:
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``high-P-rate-constant``
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An :ref:`sec-arrhenius` expression for the high-pressure limit
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``low-P-rate-constant``
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An :ref:`sec-arrhenius` expression for the low-pressure limit
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``Troe``
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Parameters for the
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`Troe <https://cantera.org/science/reactions.html#the-troe-falloff-function>`__
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falloff function. A mapping containing the keys ``A``, ``T3``, ``T1`` and
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optionally ``T2``. The default value for ``T2`` is 0.
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``SRI``
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Parameters for the
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`SRI <https://cantera.org/science/reactions.html#the-sri-falloff-function>`__
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falloff function. A mapping containing the keys ``A``, ``B``, ``C``, and
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optionally ``D`` and ``E``. The default values for ``D`` and ``E`` are 1.0
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and 0.0, respectively.
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Example::
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equation: H + CH2 (+ N2) <=> CH3 (+N2)
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type: falloff
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high-P-rate-constant: [6.00000E+14 cm^3/mol/s, 0, 0]
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low-P-rate-constant: {A: 1.04000E+26 cm^6/mol^2/s, b: -2.76, Ea: 1600}
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Troe: {A: 0.562, T3: 91, T1: 5836}
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.. _sec-chemically-activated:
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``chemically-activated``
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------------------------
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A chemically activated reaction as
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`described here <https://cantera.org/science/reactions.html#chemically-activated-reactions>`__.
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The parameters are the same as for :ref:`sec-falloff` reactions.
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Example::
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equation: CH3 + OH (+M) <=> CH2O + H2 (+M)
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type: chemically-activated
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high-P-rate-constant: [5.88E-14, 6.721, -3022.227]
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low-P-rate-constant: [282320.078, 1.46878, -3270.56495]
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.. _sec-pressure-dependent-Arrhenius:
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``pressure-dependent-Arrhenius``
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--------------------------------
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A pressure-dependent reaction using multiple Arrhenius expressions as
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`described here <https://cantera.org/science/reactions.html#pressure-dependent-arrhenius-rate-expressions-p-log>`__.
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The only additional field in this reaction type is:
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``rate-constants``
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A list of mappings, where each mapping is the mapping form of an
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:ref:`sec-arrhenius` expression with the addition of a pressure ``P``.
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Example::
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equation: H + CH4 <=> H2 + CH3
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type: pressure-dependent-Arrhenius
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rate-constants:
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- {P: 0.039474 atm, A: 2.720000e+09 cm^3/mol/s, b: 1.2, Ea: 6834.0}
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- {P: 1.0 atm, A: 1.260000e+20, b: -1.83, Ea: 15003.0}
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- {P: 1.0 atm, A: 1.230000e+04, b: 2.68, Ea: 6335.0}
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- {P: 1.01325 MPa, A: 1.680000e+16, b: -0.6, Ea: 14754.0}
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.. _sec-Chebyshev:
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``Chebyshev``
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-------------
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A reaction parameterized as a bivariate Chebyshev polynomial as
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`described here <https://cantera.org/science/reactions.html#chebyshev-reaction-rate-expressions>`__.
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Additional fields are:
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``temperature-range``
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A list of two values specifying the minimum and maximum temperatures at
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which the rate constant is valid
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``pressure-range``
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A list of two values specifying the minimum and maximum pressures at
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which the rate constant is valid
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``data``
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A list of lists containing the Chebyshev coefficients
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Example::
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equation: CH4 <=> CH3 + H
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type: Chebyshev
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temperature-range: [290, 3000]
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pressure-range: [0.0098692326671601278 atm, 98.692326671601279 atm]
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data: [[-1.44280e+01, 2.59970e-01, -2.24320e-02, -2.78700e-03],
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[ 2.20630e+01, 4.88090e-01, -3.96430e-02, -5.48110e-03],
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[-2.32940e-01, 4.01900e-01, -2.60730e-02, -5.04860e-03],
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[-2.93660e-01, 2.85680e-01, -9.33730e-03, -4.01020e-03],
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[-2.26210e-01, 1.69190e-01, 4.85810e-03, -2.38030e-03],
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[-1.43220e-01, 7.71110e-02, 1.27080e-02, -6.41540e-04]]
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.. _sec-interface-reaction:
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``interface``
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-------------
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A reaction occuring on a surface between two bulk phases, or along an edge
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at the intersection of two surfaces, as
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`described here <https://cantera.org/science/reactions.html#surface-reactions>`__.
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Includes the fields of an :ref:`sec-elementary` reaction plus:
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``sticking-coefficient``
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An :ref:`Arrhenius-type <sec-arrhenius>` expression for the sticking coefficient
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``Motz-Wise``
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A boolean applicable to sticking reactions, indicating whether to use the
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Motz-Wise correction factor for sticking coefficients near unity. Defaults
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to ``false``.
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``sticking-species``
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The name of the sticking species. Required for sticking reactions only if
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the reaction includes multiple non-surface species.
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``coverage-dependencies``
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A mapping of species names to coverage dependence parameters, where these
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parameters are contained in a mapping with the fields:
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``a``
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Coefficient for exponential dependence on the coverage
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``m``
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Power-law exponent of coverage dependence
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``E``
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Activation energy dependence on coverage
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Example::
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equation: 2 H(s) => H2 + 2 Pt(s)
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rate-constant: {A: 3.7e21 cm^2/mol/s, b: 0, Ea: 67400 J/mol}
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coverage-dependencies: {H(s): {a: 0, m: 0, E: -6000 J/mol}}
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.. _sec-electrochemical-reaction:
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``electrochemical``
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-------------------
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Interface reactions involving charge transfer between phases,
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as `described here <https://cantera.org/documentation/dev/doxygen/html/d6/ddd/classCantera_1_1ElectrochemicalReaction.html#details>`__.
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Includes the fields of an :ref:`sec-interface-reaction` reaction, plus:
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``beta``
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The symmetry factor for the reaction. Default is 0.5.
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``exchange-current-density-formulation``
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Set to ``true`` if the rate constant parameterizes the exchange current
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density. Default is ``false``.
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Example::
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equation: LiC6 <=> Li+(e) + C6
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rate-constant: [5.74, 0.0, 0.0]
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beta: 0.4
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