A core strength of the Theoretical Chemical and Quantum Physics Group

Outline

The well known Molecular Dynamics method calculates detailed trajectories for all the atoms in a simulation. Molecular Dynamics requires the use of small time steps to accurately solve the equations of motion and forces must be calculated between each pair of atoms at each time step. Consequently Molecular Dynamics can effectively only simulate a relatively small number of atoms for relatively short durations.

A popular and powerful approach to simulations involving large numbers of atoms or longer timescales or both, is the Kinetic Monte Carlo method. In Kinetic Monte Carlo the system is evolved by simulating the key atomistic processes for the system under study, in accordance with the probability of occurrence of these processes. Kinetic Monte Carlo needs to be suitably parameterised from detailed Molecular Dynamics or Ab-Initio studies. In its usual lattice approximation for atomic positions, Kinetic Monte Carlo coarse grains detailed atomic motions and avoids force calculations between pairs of atoms. This makes Kinetic Monte Carlo much cheaper computationally than Molecular Dynamics, so enabling the simulation of larger size and longer time scales compared to Molecular Dynamics. In particular Kinetic Monte Carlo can simulate the mesoscopic regime in which nanostructure growth occurs.

We have applied the Kinetic Monte Carlo method to model the development of metallic nanostructures on surfaces. Through Kinetic Monte Carlo simulations, we can investigate the influence of factors such as: adatom deposition rate, adatom mobility, substrate temperature and surface topography, on the assembly of nanostructures.

A recent Kinetic Monte Carlo study has been the growth of Pt nanostructures on Au, as potential bimetallic nano-catalysts [1].

In suitable circumstances Kinetic Monte Carlo and Molecular Dynamics can be combined together in a hybrid domain decomposition scheme, gaining benefits from each method [2].

Pt nanostructure on Au surface.

A Platinum (Pt) nanostructure (coloured silver) formed on a Gold (Au) step edge.

Recent Publications

[1] P Zoontjens, G Grochola, I K Snook and S P Russo, A Kinetic Monte Carlo study of Pt on Au(111) with applications to bimetallic catalysis, J. Phys.: Condens. Matter 23, 015302 (2011)

[2] P Zoontjens, T P Schulze and S C Hendy, Hybrid method for modelling epitaxial growth: Kinetic Monte Carlo plus Molecular Dynamics, Phys. Rev. B 76, 245418 (2007)


For more information about this technique, please contact Salvy Russo.