Tutorials

14:00 - 15:30 // Thermal spike model used for reviewing the ion-matter interaction.

The inelastic part of the energy deposited by an ion impinging a target results in defect production, defect annealing, phase transformation, local composition change, nanostructures evolution, surface change. All these results may be described using the unique concept of the thermal spike. The different energy flows are associated with the temperatures of target atomic lattice and target electrons.

Using physical data which may be collected either from experiments or theory, this model can predict the target evolution due to the passage of an ion. From the crude numerical results we propose a discussion on the way to make the link between the energy brought onto to the target atomic lattice and the ions tracks. The participants will be given the ‘instructions for use’ in order to run the simulation code.

Kai Nordlund
Helsinki University, Finland

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16:00 - 17:30 // Multiscale modelling of ion-solid interactions

I will give a tutorial of multiscale modelling of materials, focusing of aspects most relevant to ion-solid interactions. I will first overview how different kinds of simulation methods can be used to simulate different time and length scales. I will then present three methods in greater detail: binary collision approximation (BCA), molecular dynamics (MD) and kinetic Monte Carlo (KMC).

For the BCA method, I will first present the general algorithm for treating successive binary collisions, and different varieties of how it is implemented. I will also describe what its low-energy limit is, and a recent implementation of BCA for arbitrary atomic structures, suitable for simulation of Rutherford back-scattering/channeling.

I will also present the molecular dynamics (MD) method in general, and then describe special features that are needed to make the MD method suitable for efficient simulations of irradiation effects. These include recipes how to add realistic high-energy potentials, include electronic stopping, and use an adaptive time step.  I will also describe MD simulations in the recoil interaction approximation (RIA), and how such simulations can be used to get a comprehensive view of ion channeling.

Finally, I will describe the KMC approach, that allows simulating the migration of irradiation-induced defects up to macroscopic time scales. I will first present the KMC algorithm, and describe how the basic approach is very powerful as it can be considered an "exact but stochastic" simulation method. However, KMC is completely dependent of its input data set, and this limitation will be described. As a recent example I will describe recent developments of a KMC approach for simulating W fuzz formation.