Sticking species not detected correctly when ‘solid’ species are involved

[ischoegl]

Problem description

Steps to reproduce

Convert haca2.cti (CTI file pulled verbatim from Cantera 2.5.1)

Open interface as:

In [1]: import cantera as ct
   ...: 
   ...: phase = ct.Interface("haca2.yaml", "soot_interface")
---------------------------------------------------------------------------
CanteraError                              Traceback (most recent call last)
Input In [2], in <module>
      1 import cantera as ct
----> 3 phase = ct.Interface("haca2.yaml", "soot_interface")

File /work/GitHub/cantera/interfaces/cython/cantera/base.pyx:63, in cantera._cantera._SolutionBase.__cinit__()

File /work/GitHub/cantera/interfaces/cython/cantera/base.pyx:120, in cantera._cantera._SolutionBase._cinit()

File /work/GitHub/cantera/interfaces/cython/cantera/base.pyx:207, in cantera._cantera._SolutionBase._init_yaml()

CanteraError: 
*******************************************************************************
CanteraError thrown by addReactions:

*******************************************************************************
InputFileError thrown by InterfaceKinetics::buildSurfaceArrhenius:
Error on line 89 of ./haca2.yaml:
Multiple non-interface species ('CB-CB3' and 'OH')
found in sticking reaction: 'CB-CB3 + Csoot-H + OH => CO + Csoot-* + H2'.
Sticking species must be explicitly specified.
|  Line |
|    84 |   rate-constant: {A: 2.0e+13, b: 0.0, Ea: 0.0}
|    85 | - equation: Csoot-* + C2H2 => Csoot-H + H + 2 CB-CB3  # Reaction 6
|    86 |   rate-constant: {A: 8.0e+07, b: 1.56, Ea: 3.8}
|    87 | - equation: Csoot-* + O2 + 2 CB-CB3 => Csoot-* + 2 CO  # Reaction 7
|    88 |   rate-constant: {A: 2.2e+12, b: 0.0, Ea: 7.5}
>    89 > - equation: OH + Csoot-H + CB-CB3 => Csoot-* + CO + H2  # Reaction 8
            ^
|    90 |   sticking-coefficient: {A: 0.13, b: 0.0, Ea: 0.0}
*******************************************************************************
*******************************************************************************

Behavior

presumably the original CTI input file is valid (it has been part of the test suite), so it is not entirely clear what is going on … it looks like an issue with the logic in the validation of the sticking species that somehow has evaded detection: it probably should only consider gas phases?

System information

• Cantera version: 2.6.0a4
• OS: any
• Python/MATLAB/other software versions: Python 3.10 (conda)

Additional context

Issue was found when working on #1205

Resolution is contingent on #1181, and can be incorporated into #1205 [Edit: the unit test using haca2 bypasses the (newly introduced) validation step, so this issue doesn't need to be resolved for #1205]

As a reference, the sticking species is (presumably manually) added in the current ‘official’ YAML file https://github.com/Cantera/cantera/blob/main/test_problems/surfSolverTest/haca2.yaml

Possible Solutions

1. Add detection and specification of sticking species to cti2yaml
2. Only consider species that are in the gas phase in InterfaceKinetics::buildSurfaceArrhenius

I believe (2) is both more robust and easier to implement.

[speth]

The way this is handled for CTI input files is that ctml_writer does this determination if which species is in the ideal gas phase and makes the sticking species explicit in the XML file. The change in #1181 essentially mirrors this behavior, in that it will only allow sticking species from a phase that reports that it is a gas phase. However, we have a few other phase models which could in principle have sticking species, such as the Redlich-Kwong and Peng-Robinson models. Right now, these both return unspecified as the phase of matter, and so wouldn't be detected as having possible sticking species with this patch. A somewhat more permissive logic for this would be:

• If there is only one non-surface phase reactant, it is the sticking species
• If there are multiple non-surface phase reactants, but only one is in a phase identifying itself as a "gas", that is the sticking species
• Otherwise, the sticking species must be identified explicitly

[ischoegl]

@speth ... I updated the check in #1181 per your suggestions.