** ** Joseph Salaris (Radboud University, Department of Theoretical Chemistry)

* Application of the kinetic Monte Carlo method to simulate the evolution of interstellar ice layers *
Friday, 27 January 2023, 10:00-11:00 in HG03.085

### Abstract

Molecular clouds are the birthplace of new stars and consist of gas and dust. The dust refers
to nanosized grains which provide a surface for molecules to form on. However, the first models
used by astrochemists were pure gas-models, using deterministic chemical rate equations (set of
coupled ordinary differential equations) and they were able to explain the observed molecular
abundancies with partial success. In my talk, I will briefly motivate the study of molecules in
space and the advantage of stochastic methods to model molecule formation. The latter has
everything to do with the incorporation of the dust grain surface chemistry in the models. I
will focus on a class of stochastic simulation methods that have become known as kinetic Monte
Carlo (KMC) methods. After outlining the theory behind the (standard) KMC approach using
the formation of H2 as an example, I will go over some KMC algorithms as implemented in our
Theoretical & Computational Chemistry group. Next, I will discuss the challenges we face using
the KMC method with the simulation of molecular chemistry on dust grain surfaces. Finally, I
will pose some mathematical questions that we have, regarding the different implementations of
the KMC method and stochastic simulation in general.

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