# Question about kinetic surface model

**URL:** <https://festim.discourse.group/t/question-about-kinetic-surface-model/185>\
**Category:** User Support\
**Tags:** festim2\
**Created:** [September 8, 2026, 3:19am UTC](https://festim.discourse.group/t/question-about-kinetic-surface-model/185 "2026-09-08T03:19:13Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![williamhayes123](https://yyz2.discourse-cdn.com/free1/user_avatar/festim.discourse.group/williamhayes123/32/287_2.png) [@williamhayes123](https://festim.discourse.group/u/williamhayes123)\
**Post date:** [September 8, 2026, 3:19am UTC](https://festim.discourse.group/t/question-about-kinetic-surface-model/185/1 "2026-09-08T03:19:13Z")

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In FESTIM verification, surface kinetic model gives the code like that,  
F.SurfaceKinetics(  
k\_sb=k\_sb,  
k\_bs=k\_bs,  
lambda\_IS=lambda\_IS,  
n\_surf=n\_surf,  
n\_IS=n\_IS,  
J\_vs=J\_vs,  
surfaces=1,  
initial\_condition=exact\_solution\_cs(t=0),  
t=F.t,  
),

but this setting is only available in festim1.4, but not found in the festim2 api.

why kinetic surface model is absent for festim new version?

Can alll boundary conditions be set as the plasma dirven permeation case?

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<div class="post-metadata">

**Author:** ![remidm](https://yyz2.discourse-cdn.com/free1/user_avatar/festim.discourse.group/remidm/32/4_2.png) [@remidm](https://festim.discourse.group/u/remidm)\
**Post date:** [September 8, 2026, 2:54pm UTC](https://festim.discourse.group/t/question-about-kinetic-surface-model/185/2 "2026-09-08T14:54:51Z")

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Hi @williamhayes123 and welcome to the FESTIM discourse 🎉

Indeed, this surface kinetics model is not implemented in FESTIM2. The reason for that is that FESTIM1 used `RealElements` in legacy-fenics, which until very recently were not available in FEniCSx.

However, with the (very) recent developments coming up to `v2.2` (currently available as a pre-release `v2.2rc.2`), we introduced _manifolds_ which will allow to simulate surface kinetics.

You can find the relevant tutorials there: [Manifold subdomains — FESTIM tutorial](https://festim-workshop.readthedocs.io/en/latest/content/manifolds/index.html)

Depending on your actual problem, you may not need the full kinetic surface model if the rates are fast enough and you could get away with dissociation/recombination fluxes instead.

Happy to discuss more