Modeling Large Catalyst Systems Using Classical Mechanics

Modeling Large Catalyst Systems Using Classical Mechanics 

Thanks to their speed and relatively low computational cost, M D and MC simulations can be used for studying the physical properties of large systems. This is extremely useful in heterogeneous catalysis, e.g., for modeling the structure and the properties of the bulk and the surface of a solid catalyst, or the properties of the bulk and interface of liquid/liquid biphasic systems. However, since the number of particles modeled is still very small compared to real materials, the models are susceptible to wall effects. One neat trick for avoiding this problem is to apply periodic boundary conditions The volume containing the model is treated as the primitive cell of an 

---

The cluster model approach assumes that a limited number of atoms can be used to represent the catalyst active site. Ideally, one would like to include a few thousands atoms in the model so that the cluster boundary is sufficiently far from the cluster active site thus ensuring that edge effects are of minor importance and can be neglected. Unfortunately, the computational effort of an ab initio calculation grows quite rapidly with the number of atoms treated quantum mechanically and cluster models used in practice contain 20 to 50 atoms only. It is well possible that with the advent of the N-scaling methods " this number can dramatically increase. Likewise, the use of hybrid methods able to decompose a very large system in two subsets that are then treated at different level of accuracy, or define a quantum mechanical and a classical part, are also very promising. However, its practical implementation for metallic systems remains still indeterminate. 

---