Cantera/CTI Files/Reactions - Revision history

Admin: Fix Arrhenius surface kinetics equation: add missing negative sign in exponent (exp(-E/RT), not exp(E/RT)) (via update-page on MediaWiki MCP Server)

2026-06-14T23:30:56Z

Fix Arrhenius surface kinetics equation: add missing negative sign in exponent (exp(-E/RT), not exp(E/RT)) (via update-page on MediaWiki MCP Server)

← Older revision		Revision as of 23:30, 14 June 2026
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	<math>		<math>
	k = A T^b \exp \left( \frac{E}{RT} \right)		k = A T^b \exp \left( -\frac{E}{RT} \right)
	</math>		</math>

Admin: /* Sticking Surface Reactions Code */

2017-04-17T08:45:29Z

Sticking Surface Reactions Code

← Older revision		Revision as of 08:45, 17 April 2017
Line 256:		Line 256:
	===Sticking Surface Reactions Code===		===Sticking Surface Reactions Code===

	~~Dunno~~		To do

	==Surface Reactions with Falloff==		==Surface Reactions with Falloff==

Admin at 08:44, 17 April 2017

2017-04-17T08:44:42Z

← Older revision		Revision as of 08:44, 17 April 2017
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	Main ~~Cantera page on CTI files: [[~~Cantera/CTI Files]]		{{Main\|Cantera/CTI Files}}

	=Reaction Specification=		=Reaction Specification=
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	~~[[Category:Cantera]]~~
			=Flags=

			{{CanteraFlag}}

Admin: /* Reaction Specification */

2014-01-29T23:16:17Z

Reaction Specification

← Older revision		Revision as of 23:16, 29 January 2014
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	=Reaction Specification=		=Reaction Specification=

	Processing of reactions in CTI files occurs in the file <code>ctml_writer.py</code>, located in <code>cantera/interfaces/python/ctml_writer.py</code>. This class is defined around line 968 or so:		Processing of reactions in CTI files occurs in the file <code>ctml_writer.py</code>, located in <code>cantera/interfaces/python/ctml_writer.py</code>. This class is defined around line 968 or so.

	~~<source lang="python">~~		The file uses special notation for things that the CTI interpreter knows how to understand. For example, the reaction direction can be specified using different symbols:
	~~class~~ reaction:		forward reactions are specified using <code>=></code>, reverse reactions are specified using <code><=</code>, and reversible reactions are specified using <code><=></code>, like this:
	~~[...]~~
	~~</source>~~

	~~Forward~~ reactions are specified using <code>=></code>, reverse reactions are specified using <code><=</code>, and reversible reactions are specified using <code><=></code>, like this:

	<pre>		<pre>

Admin: /* Reaction Specification */

2014-01-29T23:12:24Z

Reaction Specification

← Older revision		Revision as of 23:12, 29 January 2014
Line 2:		Line 2:

	=Reaction Specification=		=Reaction Specification=

			Processing of reactions in CTI files occurs in the file <code>ctml_writer.py</code>, located in <code>cantera/interfaces/python/ctml_writer.py</code>. This class is defined around line 968 or so:

			<source lang="python">
			class reaction:
			[...]
			</source>

			Forward reactions are specified using <code>=></code>, reverse reactions are specified using <code><=</code>, and reversible reactions are specified using <code><=></code>, like this:

			<pre>
			A + B => C
			G <= E + F
			W + X <=> Y + Z
			</pre>

	=Gas Reactions=		=Gas Reactions=

Admin at 23:07, 29 January 2014

2014-01-29T23:07:48Z

← Older revision		Revision as of 23:07, 29 January 2014
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	</pre>		</pre>

	==Surface Reactions==		=Surface Reactions=

	Any surface reaction can be specified in the cti file using the <code>surface_reaction</code> function. The usage depends on the surface reaction form.		Any surface reaction can be specified in the cti file using the <code>surface_reaction</code> function. The usage depends on the surface reaction form.

Admin at 23:07, 29 January 2014

2014-01-29T23:07:34Z

← Older revision		Revision as of 23:07, 29 January 2014
Line 3:		Line 3:
	=Reaction Specification=		=Reaction Specification=

	==Gas Reactions==		=Gas Reactions=

	An example gas reaction CTI file is located at <code>cantera/data/inputs/h2o2.cti</code>.		An example gas reaction CTI file is located at <code>cantera/data/inputs/h2o2.cti</code>.
Line 15:		Line 15:
	where <math>\nu_{ij}</math> is the stoichiometric coefficient for species i in reaction j, <math>c_i</math> is the molar concentration of species i, and <math>n_{ij}</math> is the order of reaction j with respect to species i.		where <math>\nu_{ij}</math> is the stoichiometric coefficient for species i in reaction j, <math>c_i</math> is the molar concentration of species i, and <math>n_{ij}</math> is the order of reaction j with respect to species i.

	===Arrhenius Gas Kinetics===		==Arrhenius Gas Kinetics==

	The standard way to model reaction kinetics in the gas phase is to use Arrhenius kinetics. This models the reaction rate constant <math>k_j</math> as:		The standard way to model reaction kinetics in the gas phase is to use Arrhenius kinetics. This models the reaction rate constant <math>k_j</math> as:
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	* <math>E_j</math> - specified in units of <math>\frac{ \text{cal} }{ \text{mol} }</math>		* <math>E_j</math> - specified in units of <math>\frac{ \text{cal} }{ \text{mol} }</math>

	====Arrhenius Gas Kinetics Example====		===Arrhenius Gas Kinetics Example===

	'''Example:'''		'''Example:'''
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	</pre>		</pre>

	====Arrhenius Gas Kinetics Code====		===Arrhenius Gas Kinetics Code===

	More information on what blocks of code process this stuff from the CTI file.		More information on what blocks of code process this stuff from the CTI file.

	===Three-Body Gas Reactions===		==Three-Body Gas Reactions==

	A three body gas reaction is... I don't know.		A three body gas reaction is... I don't know.
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	</pre>		</pre>

	====Three Body Gas Reactions Example====		===Three Body Gas Reactions Example===

	It would help if I could figure out what this reaction type is, before putting together an example.		It would help if I could figure out what this reaction type is, before putting together an example.

	====Three Body Gas Reactions Code====		===Three Body Gas Reactions Code===

	When Cantera processes a CTI file, it determines what kind of kinetics object to use. If the kinetics is for a gas phase, the object is a GasKinetics object. The GasKinetics object has a <code>GasKinetics::addReaction()</code> method, which is run for each reaction in the CTI file:		When Cantera processes a CTI file, it determines what kind of kinetics object to use. If the kinetics is for a gas phase, the object is a GasKinetics object. The GasKinetics object has a <code>GasKinetics::addReaction()</code> method, which is run for each reaction in the CTI file:
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	</source>		</source>

	===Falloff Gas Reactions===		==Falloff Gas Reactions==

	<pre>		<pre>
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	</pre>		</pre>

	====Falloff Gas Reaction Example====		===Falloff Gas Reaction Example===

	====Falloff Gas Reaction Code====		===Falloff Gas Reaction Code===

	===Other Gas Reaction Options===		==Other Gas Reaction Options==

	Duplicate is the only option I see:		Duplicate is the only option I see:
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	An example surface reaction CTI file is located at <code>cantera/data/inputs/ptcombust.cti</code>.		An example surface reaction CTI file is located at <code>cantera/data/inputs/ptcombust.cti</code>.

	===Arrhenius Surface Kinetics===		==Arrhenius Surface Kinetics==

	The plain/default way, which uses Arrhenius kinetics:		The plain/default way, which uses Arrhenius kinetics:
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	</math>		</math>

	====Arrhenius Surface Kinetics Example====		===Arrhenius Surface Kinetics Example===

	A catalytic reaction where H2O (adsorbed onto a platinum surface) desorbs would look like this:		A catalytic reaction where H2O (adsorbed onto a platinum surface) desorbs would look like this:
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	</pre>		</pre>

	====Arrhenius Surface Kinetics Code====		===Arrhenius Surface Kinetics Code===

	Not sure where this is dealt with in the Cantera code.		Not sure where this is dealt with in the Cantera code.

	===Surface Reactions with Coverage-Dependent Rates===		==Surface Reactions with Coverage-Dependent Rates==

	Still working through this coverage dependency.		Still working through this coverage dependency.
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	</pre>		</pre>

	===Surface Reactions with Sticking Equations===		==Surface Reactions with Sticking Equations==

	No idea how this works.		No idea how this works.
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	</pre>		</pre>

	====Sticking Surface Reactions Example====		===Sticking Surface Reactions Example===

	<pre>		<pre>
Line 243:		Line 243:
	</pre>		</pre>

	====Sticking Surface Reactions Code====		===Sticking Surface Reactions Code===

	Dunno		Dunno

	===Surface Reactions with Falloff===		==Surface Reactions with Falloff==

	No idea.		No idea.

	====Surface Reactions with Falloff Example====		===Surface Reactions with Falloff Example===

	To do		To do

	====Surface Reactions with Falloff Code====		===Surface Reactions with Falloff Code===

	To do		To do

	===Other Surface Reaction Options===		==Other Surface Reaction Options==

	<pre>		<pre>

Admin at 22:17, 29 January 2014

2014-01-29T22:17:01Z

← Older revision		Revision as of 22:17, 29 January 2014
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	options = 'duplicate')		options = 'duplicate')
	</pre>		</pre>


			[[Category:Cantera]]

Admin: Created page with "Main Cantera page on CTI files: Cantera/CTI Files =Reaction Specification= ==Gas Reactions== An example gas reaction CTI file is located at `cantera/data/inputs/h2o2...."`


2014-01-29T22:16:02Z
Created page with "Main Cantera page on CTI files: Cantera/CTI Files  =Reaction Specification=  ==Gas Reactions==  An example gas reaction CTI file is located at <code>cantera/data/inputs/h2o2...."
New page
Main Cantera page on CTI files: [[Cantera/CTI Files]]



=Reaction Specification=



==Gas Reactions==



An example gas reaction CTI file is located at <code>cantera/data/inputs/h2o2.cti</code>.



In general, the gas phase reaction rate can be modeled as:



<math>

r_{j} = k_j \sum_{i} \nu_{ij} c_{i}^{n_{ij}}

</math>



where <math>\nu_{ij}</math> is the stoichiometric coefficient for species i in reaction j, <math>c_i</math> is the molar concentration of species i, and <math>n_{ij}</math> is the order of reaction j with respect to species i.



===Arrhenius Gas Kinetics===



The standard way to model reaction kinetics in the gas phase is to use Arrhenius kinetics. This models the reaction rate constant <math>k_j</math> as:



<math>

k_j = A_j T^{b_j} \exp \left( - \dfrac{ E_j }{ RT } \right)

</math>



where the Arrhenius reaction parameters are:

* <math>A_j</math> - Arrhenius parameter pre-exponential factor

* <math>b_j</math> - Arrhenius parameter, degree of temperature influence on kinetic rate constant

* <math>E_j</math> - Arrhenius parameter, activation energy of reaction



These quantities can be specified in a CTI file as follows:



<pre>

reaction(  "A + B => C + D",  [A, b, E] )

</pre>



and the units of each are:

* <math>A_j</math> - specified in units of <math>\frac{ \text{cm}^3 }{ \text{mol} \cdot \text{s} }</math>

* <math>b_j</math> - dimensionless

* <math>E_j</math> - specified in units of <math>\frac{ \text{cal} }{ \text{mol} }</math>



====Arrhenius Gas Kinetics Example====



'''Example:'''



Specify the reaction 



<math>

\text{H} + \text{O}_2 \rightarrow \text{O} + \text{OH}

</math>



which has the following parameter values:



<math>

A = 3.54700E+15 \quad \frac{ \text{cm}^3 }{ \text{mol} \cdot \text{s} }

</math>



<math>

b = -0.406

</math>



<math>

E = 16599 \quad \frac{ \text{cal} }{ \text{mol} }

</math>



'''Result:'''



<pre>

reaction(  "H + O2 <=> O + OH",  [3.54700E+15, -0.406, 16599])

</pre>



====Arrhenius Gas Kinetics Code====



More information on what blocks of code process this stuff from the CTI file.



===Three-Body Gas Reactions===



A three body gas reaction is... I don't know.



<pre>

three_body_reaction( "H2 + M <=> H + H + M",  [4.57700E+19, -1.4, 104380],

         efficiencies = " AR:0  CO:1.9  CO2:3.8  H2:2.5  H2O:12  HE:0 ")

</pre>



====Three Body Gas Reactions Example====



It would help if I could figure out what this reaction type is, before putting together an example.



====Three Body Gas Reactions Code====



When Cantera processes a CTI file, it determines what kind of kinetics object to use. If the kinetics is for a gas phase, the object is a GasKinetics object. The GasKinetics object has a <code>GasKinetics::addReaction()</code> method, which is run for each reaction in the CTI file:



<source lang="cpp">

void GasKinetics::

addReaction(ReactionData& r)

{

    switch (r.reactionType) {

    case ELEMENTARY_RXN:

        addElementaryReaction(r);

        break;

    case THREE_BODY_RXN:

        addThreeBodyReaction(r);

        break;

    case FALLOFF_RXN:

        addFalloffReaction(r);

        break;

    case PLOG_RXN:

        addPlogReaction(r);

        break;

    case CHEBYSHEV_RXN:

        addChebyshevReaction(r);

        break;

    default:

        throw CanteraError("GasKinetics::addReaction", "Invalid reaction type specified");

    }

</source>



The three body reaction computation is set up in <code>GasKinetics::addThreeBodyReaction</code>:



<source lang="cpp">

void GasKinetics::

addThreeBodyReaction(ReactionData& r)

{

    // install rate coeff calculator

    size_t iloc = m_rates.install(reactionNumber(), r);



    // add constant term to rate coeff value vector

    m_rfn.push_back(r.rateCoeffParameters[0]);



    // forward rxn order equals number of reactants + 1

    m_fwdOrder.push_back(r.reactants.size() + 1);



    m_3b_concm.install(reactionNumber(), r.thirdBodyEfficiencies,

                       r.default_3b_eff);

    registerReaction(reactionNumber(), THREE_BODY_RXN, iloc);

}

</source>



===Falloff Gas Reactions===



<pre>

falloff_reaction( "H + O2 (+ M) <=> HO2 (+ M)",

         kf = [1.47500E+12, 0.6, 0],

         kf0   = [6.36600E+20, -1.72, 524.8],

         falloff = Troe(A = 0.8, T3 = 1e-30, T1 = 1e+30),

         efficiencies = " CO:1.9  CO2:3.8  H2:2  H2O:11  O2:0.78 ")

</pre>



====Falloff Gas Reaction Example====



====Falloff Gas Reaction Code====



===Other Gas Reaction Options===



Duplicate is the only option I see:



<pre>

reaction(  "HO2 + HO2 <=> H2O2 + O2",  [1.30000E+11, 0, -1629.3],

         options = ["duplicate"])

</pre>



==Surface Reactions==



Any surface reaction can be specified in the cti file using the <code>surface_reaction</code> function. The usage depends on the surface reaction form.



There are a variety of forms of surface reactions, each with a different specification method.



An example surface reaction CTI file is located at <code>cantera/data/inputs/ptcombust.cti</code>.



===Arrhenius Surface Kinetics===



The plain/default way, which uses Arrhenius kinetics:



<pre>

surface_reaction( "A(s) => B(s) + C",   [A, b, E]) 

</pre>



where:

* A(s), B(s), C - species whose properties are defined in the species section (see above)

* A - Arrhenius parameter, pre-exponential factor (specified in units of...)

* b - Arrhenius parameter, degree of temperature influence on kinetic rate constant

* E - Arrhenius parameter, activation energy of reaction



The Arrhenius expression is:



<math>

k = A T^b \exp \left( \frac{E}{RT} \right)

</math>



====Arrhenius Surface Kinetics Example====



A catalytic reaction where H2O (adsorbed onto a platinum surface) desorbs would look like this:



<pre>

surface_reaction( "H2O(S) => H2O + PT(S)",   [1.00000E+13, 0, 40300])

</pre>



====Arrhenius Surface Kinetics Code====



Not sure where this is dealt with in the Cantera code.



===Surface Reactions with Coverage-Dependent Rates===



Still working through this coverage dependency.



This uses some kind of expression containing a, m, and e.



<pre>

surface_reaction( "A(s) => B(s) + C", Arrhenius(A, b, E, coverage=['A(s)', surface_a, surface_m, surface_e])

</pre>



Attempting to uncover how this is dealt with:



<pre>

importKinetics::getCoverageDependence()

rdata.cov vector contains coverage-related parameters/information

rdata.cov.push_back(species_index)

rdata.cov.push_back(a)

rdata.cov.push_back(m)

rdata.cov.push_back(e)

</pre>



and then



<pre>

InterfaceKinetics::addElementaryReaction

if r.cov.size > 3:

    this rxn is dependent on coverage

register rxn

</pre>



===Surface Reactions with Sticking Equations===



No idea how this works.



<pre>

surface_reaction( "A + B(s) => C + D(s)",   stick(1.00000E+00, 0, 0))

</pre>



====Sticking Surface Reactions Example====



<pre>

surface_reaction( "OH + PT(S) => OH(S)",   stick(1.00000E+00, 0, 0))

</pre>



====Sticking Surface Reactions Code====



Dunno



===Surface Reactions with Falloff===



No idea.



====Surface Reactions with Falloff Example====



To do



====Surface Reactions with Falloff Code====



To do



===Other Surface Reaction Options===



<pre>

surface_reaction( "O2 + 2 PT(S) => 2 O(S)",   Arrhenius(1.80000E+21, -0.5, 0),

                  options = 'duplicate')

</pre>

Cantera/CTI Files/Reactions - Revision history

Admin: Fix Arrhenius surface kinetics equation: add missing negative sign in exponent (exp(-E/RT), not exp(E/RT)) (via update-page on MediaWiki MCP Server)

Admin: /* Sticking Surface Reactions Code */

Admin at 08:44, 17 April 2017

Admin: /* Reaction Specification */

Admin: /* Reaction Specification */

Admin at 23:07, 29 January 2014

Admin at 23:07, 29 January 2014

Admin at 22:17, 29 January 2014

Admin: Created page with "Main Cantera page on CTI files: Cantera/CTI Files =Reaction Specification= ==Gas Reactions== An example gas reaction CTI file is located at cantera/data/inputs/h2o2...."

Admin: Created page with "Main Cantera page on CTI files: Cantera/CTI Files =Reaction Specification= ==Gas Reactions== An example gas reaction CTI file is located at `cantera/data/inputs/h2o2...."`