Hybrid modeling of associative thermal desorption

The article examines a hybrid multi-scale numerical algorithm that models surface reactions in the framework of the lattice gas model allowing for lateral interaction between adsorbed particles. The model is called Quasi-Equilibrium Kinetic Monte-Carlo (QE-KMC) algorithm. QE-KMC combines stochastic Monte-Carlo calculations (the Metropolis algorithm) with standard numerical methods for deterministic ordinary differential equations (ODE). QE-KMC assumes “infinitely fast” diffusion of absorbed particles on the lattice, which permits describing the macroscopic dynamics of the system by ODE for mean concentrations. These equations are not specified explicitly, but we can nevertheless evaluate their right-hand sides with prescribed accuracy by the Metropolis method. In the present article, QE-KMC is applied to generate associative thermal desorption spectra (TDS). TDS are presented for typical parameter values of lateral interactions on a square and hexagonal lattices. The QE-KMC results are compared with standard Kinetic Monte Carlo (KMC) results for lattice systems. We show that QE-KMC and KMC methods produce identical results if KMC allows for very fast surface diffusion. Yet QE-KMC requires much less computing time.