Reactions#
The fields common to all reaction entries are:
equationThe stoichiometric equation for the reaction. Each term (that is, stoichiometric coefficient, species name,
+or<=>) in the equation must be separated by a space.Reversible reactions may be written using
<=>or=to separate reactants and products. Irreversible reactions are written using=>.typeA string specifying the type of reaction or rate coefficient parameterization. The default is
elementary. Reaction types are:elementary(details)three-body(details)Blowers-Masel(details)two-temperature-plasma(details)falloff(details)chemically-activated(details)pressure-dependent-Arrhenius(details)Chebyshev(details)
Reactions without a specified
typeon surfaces or edges are automatically treated as interface-Arrhenius reactions, unless asticking-coefficientimplies a sticking-Arrhenius reaction. Interface reactions that involve charge transfer between phases are automatically treated as electrochemical reactions.Reactions on surfaces or edges specifying
typeasBlowers-Maselare treated as interface-Blowers-Masel or sticking-Blowers-Masel.duplicateBoolean indicating whether the reaction is a known duplicate of another reaction. The default is
false.ordersAn optional mapping of species to explicit reaction orders to use. Reaction orders for reactant species not explicitly mentioned are taken to be their respective stoichiometric coefficients. See Reaction orders for additional information.
negative-ordersBoolean indicating whether negative reaction orders are allowed. The default is
false.nonreactant-ordersBoolean indicating whether orders for non-reactant species are allowed. The default is
false.
Depending on the reaction type, other fields may be necessary to specify
the rate of the reaction.
Reaction rate expressions#
Arrhenius#
Arrhenius rate expressions are specified as a mapping with fields:
AThe pre-exponential factor \(A\)
bThe temperature exponent \(b\)
EaThe activation energy \(E_a\)
or a corresponding three-element list. The following are equivalent:
{A: -2.70000E+13 cm^3/mol/s, b: 0, Ea: 355 cal/mol}
[-2.70000E+13 cm^3/mol/s, 0, 355 cal/mol]
Blowers-Masel#
Blowers-Masel rate expressions calculate the rate constant based on the Blowers Masel approximation as described here. The rate parameters are specified as a mapping with fields:
AThe pre-exponential factor \(A\)
bThe temperature exponent \(b\)
Ea0The intrinsic activation energy \(E_{a0}\)
wThe average of the bond dissociation energy of the bond breaking and that being formed in the reaction \(w\)
or a corresponding four-element list. The following are equivalent:
{A: 3.87e+04 cm^3/mol/s, b: 2.7, Ea0: 6260.0 cal/mol, w: 1e9 cal/mol}
[3.87e+04 cm^3/mol/s, 2.7, 6260.0 cal/mol, 1e9 cal/mol]
Two-Temperature Plasma#
Two-temperature plasma reactions involve an electron as one of the reactants, where the electron temperature may differ from the gas temperature as described here. The rate parameters are specified as a mapping with fields:
AThe pre-exponential factor
bThe temperature exponent, which is applied to the electron temperature
Ea-gasThe activation energy term \(E_{a,g}\) that is related to the gas temperature
Ea-electronThe activation energy term \(E_{a,e}\) that is related to the electron temperature
or a corresponding four-element list. The following are equivalent:
{A: 17283, b: -3.1, Ea-gas: -5820 J/mol, Ea-electron: 1081 J/mol}
[17283, -3.1, -5820 J/mol, 1081 J/mol]
Efficiencies#
Some reaction types include parameters for the “efficiency” of different species as third-body colliders. For these reactions, the following additional fields are supported:
efficienciesA mapping of species names to efficiency values
default-efficiencyThe efficiency for use for species not included in the
efficienciesmapping. Defaults to 1.0.
Reaction types#
elementary#
A homogeneous reaction with a pressure-independent rate coefficient and mass action kinetics, as described here.
Additional fields are:
rate-constantAn Arrhenius-type list or mapping.
negative-AA boolean indicating whether a negative value for the pre-exponential factor is allowed. The default is
false.
Example:
equation: N + NO <=> N2 + O
rate-constant: {A: -2.70000E+13 cm^3/mol/s, b: 0, Ea: 355 cal/mol}
negative-A: true
three-body#
A three body reaction as described here.
The reaction equation should include the third body collision partner M.
Includes the fields of an elementary reaction, plus the fields for
specifying efficiencies.
Example:
equation: 2 O + M = O2 + M
type: three-body
rate-constant: [1.20000E+17 cm^6/mol^2/s, -1, 0]
efficiencies: {AR: 0.83, H2O: 5}
Blowers-Masel#
Includes the fields of an elementary reaction, except that
the rate-constant field is a
Blowers-Masel-type list or mapping.
Example:
equation: O + H2 <=> H + OH
type: Blowers-Masel
rate-constant: {A: 3.87e+04 cm^2/mol/s, b: 2.7, Ea0: 6260.0 cal/mol, w: 1e9 cal/mol}
two-temperature-plasma#
Includes the fields of an elementary reaction, except that
the rate-constant field is a
Two-temperature-plasma-type list or
mapping.
Example:
equation: O + H => O + H
type: two-temperature-plasma
rate-constant: {A: 17283, b: -3.1, Ea-gas: -5820 J/mol, Ea-electron: 1081 J/mol}
falloff#
A falloff reaction as described here.
The reaction equation should include the pressure-dependent third body collision
partner (+M) or (+name) where name is the name of a species. The
latter case is equivalent to setting the efficiency for name to 1 and the
efficiency for all other species to 0.
Includes field for specifying efficiencies as well as:
high-P-rate-constantAn Arrhenius expression for the high-pressure limit
low-P-rate-constantAn Arrhenius expression for the low-pressure limit
TroeParameters for the Troe falloff function. A mapping containing the keys
A,T3,T1and optionallyT2. The default value forT2is 0.SRIParameters for the SRI falloff function. A mapping containing the keys
A,B,C, and optionallyDandE. The default values forDandEare 1.0 and 0.0, respectively.TsangParameters for the Tsang falloff function. A mapping containing the keys
AandB. The default value forBis 0.0.
Example:
equation: H + CH2 (+ N2) <=> CH3 (+N2)
type: falloff
high-P-rate-constant: [6.00000E+14 cm^3/mol/s, 0, 0]
low-P-rate-constant: {A: 1.04000E+26 cm^6/mol^2/s, b: -2.76, Ea: 1600}
Troe: {A: 0.562, T3: 91, T1: 5836}
chemically-activated#
A chemically activated reaction as described here.
The parameters are the same as for falloff reactions.
Example:
equation: CH3 + OH (+M) <=> CH2O + H2 (+M)
type: chemically-activated
high-P-rate-constant: [5.88E-14, 6.721, -3022.227]
low-P-rate-constant: [282320.078, 1.46878, -3270.56495]
pressure-dependent-Arrhenius#
A pressure-dependent reaction using multiple Arrhenius expressions as described here.
The only additional field in this reaction type is:
rate-constantsA list of mappings, where each mapping is the mapping form of an Arrhenius expression with the addition of a pressure
P.
Example:
equation: H + CH4 <=> H2 + CH3
type: pressure-dependent-Arrhenius
rate-constants:
- {P: 0.039474 atm, A: 2.720000e+09 cm^3/mol/s, b: 1.2, Ea: 6834.0}
- {P: 1.0 atm, A: 1.260000e+20, b: -1.83, Ea: 15003.0}
- {P: 1.0 atm, A: 1.230000e+04, b: 2.68, Ea: 6335.0}
- {P: 1.01325 MPa, A: 1.680000e+16, b: -0.6, Ea: 14754.0}
Chebyshev#
A reaction parameterized as a bivariate Chebyshev polynomial as described here.
Additional fields are:
temperature-rangeA list of two values specifying the minimum and maximum temperatures at which the rate constant is valid
pressure-rangeA list of two values specifying the minimum and maximum pressures at which the rate constant is valid
dataA list of lists containing the Chebyshev coefficients
Example:
equation: CH4 <=> CH3 + H
type: Chebyshev
temperature-range: [290, 3000]
pressure-range: [0.0098692326671601278 atm, 98.692326671601279 atm]
data: [[-1.44280e+01, 2.59970e-01, -2.24320e-02, -2.78700e-03],
[ 2.20630e+01, 4.88090e-01, -3.96430e-02, -5.48110e-03],
[-2.32940e-01, 4.01900e-01, -2.60730e-02, -5.04860e-03],
[-2.93660e-01, 2.85680e-01, -9.33730e-03, -4.01020e-03],
[-2.26210e-01, 1.69190e-01, 4.85810e-03, -2.38030e-03],
[-1.43220e-01, 7.71110e-02, 1.27080e-02, -6.41540e-04]]
interface-Arrhenius#
A reaction occurring on a surface between two bulk phases, or along an edge at the intersection of two surfaces, as described here.
Includes the fields of an elementary reaction plus:
coverage-dependenciesA mapping of species names to coverage dependence parameters, where these parameters are contained in either a mapping with the fields:
aCoefficient for exponential dependence on the coverage
mPower-law exponent of coverage dependence
EActivation energy dependence on coverage, which uses the same sign convention as the leading-order activation energy term. This can be a scalar value for the linear dependency or a list of four values for the polynomial dependency given in the order of 1st, 2nd, 3rd, and 4th-order coefficients
or a list containing the three elements above, in the given order.
Note that parameters
a,mandEcorrespond to parameters \(\eta_{ki}\), \(\mu_{ki}\) and \(\epsilon_{ki}\) in Eq 11.113 of [Kee, R. J., Coltrin, M. E., & Glarborg, P.(2003). Chemically reacting flow: theory and practice. John Wiley & Sons], respectively.
Examples:
- equation: 2 H(s) => H2 + 2 Pt(s)
rate-constant: {A: 3.7e21 cm^2/mol/s, b: 0, Ea: 67400 J/mol}
coverage-dependencies: {H(s): {a: 0, m: 0, E: -6000 J/mol}}
- equation: 2 O(S) => O2 + 2 Pt(S)
rate-constant: {A: 3.7e+21, b: 0, Ea: 213200 J/mol}
coverage-dependencies: {O(S): {a: 0.0, m: 0.0,
E: [1.0e3 J/mol, 3.0e3 J/mol , -7.0e4 J/mol , 5.0e3 J/mol]}
- equation: CH4 + PT(S) + O(S) => CH3(S) + OH(S)
rate-constant: {A: 5.0e+18, b: 0.7, Ea: 4.2e+04}
coverage-dependencies:
O(S): [0, 0, 8000]
PT(S): [0, -1.0, 0]
- equation: 2 O(S) => O2 + 2 Pt(S)
rate-constant: {A: 3.7e+21, b: 0, Ea: 213200 J/mol}
coverage-dependencies:
O(S): [0, 0, [1.0e6, 3.0e6, -7.0e7, 5.0e6]]
interface-Blowers-Masel#
Includes the same fields as interface-Arrhenius, while using the Blowers-Masel parameterization for the rate constant.
Example:
equation: 2 H(s) => H2 + 2 Pt(s)
type: Blowers-Masel
rate-constant: {A: 3.7e21 cm^2/mol/s, b: 0, Ea0: 67400 J/mol, w: 1000000 J/mol}
coverage-dependencies: {H(s): {a: 0, m: 0, E: -6000 J/mol}}
sticking-Arrhenius#
A sticking reaction occurring on a surface adjacent to a bulk phase, as described here.
Includes the fields of an interface-Arrhenius reaction plus:
sticking-coefficientAn Arrhenius-type expression for the sticking coefficient
Motz-WiseA boolean indicating whether to use the Motz-Wise correction factor for sticking coefficients near unity. Defaults to
false.sticking-speciesThe name of the sticking species. Required if the reaction includes multiple non-surface species.
Example:
equation: OH + PT(S) => OH(S)
sticking-coefficient: {A: 1.0, b: 0, Ea: 0}
sticking-Blowers-Masel#
Includes the same fields as sticking-Arrhenius, while using the Blowers-Masel parameterization for the sticking coefficient.
Example:
equation: OH + PT(S) => OH(S)
type: Blowers-Masel
sticking-coefficient: {A: 1.0, b: 0, Ea0: 0, w: 100000}
Motz-Wise: true
electrochemical#
Interface reactions involving charge transfer between phases.
Includes the fields of an interface-Arrhenius reaction, plus:
betaThe symmetry factor for the reaction. Default is 0.5.
exchange-current-density-formulationSet to
trueif the rate constant parameterizes the exchange current density. Default isfalse.
Example:
equation: LiC6 <=> Li+(e) + C6
rate-constant: [5.74, 0.0, 0.0]
beta: 0.4