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Supervised theses

Thermodynamik binärer entmischender Legierungen - Cluster Variation Method und Monte Carlo Simulationen

This is the bachelor's thesis of Markus Macher, submitted in January 2011. It is an investigation of the thermodynamics of phase-separating crystallic systems on a number of lattices. The energetics are described by nearest-neighbour pair interactions leading to phase separation. The resulting phase diagram is computed both theoretically with the Cluster Variation Method with increasing degrees of accuracy and by Monte-Carlo simulations.

It addresses two points of interest: it shows the influence of the dimension of the lattice and of the coordination number on the form of the resulting phase diagram, and it shows that the accuracy obtained with the Cluster Variation Method with a given size of the fundamental cluster also depends strongly on the lattice studied. It is available here (in german).

Studies of atomic diffusion in NiPt by X-ray photon correlation spectroscopy

This is the diploma thesis of Markus Stana, submitted in June 2011. It documents his first results in applying the main experimental method of our group, X-ray photon correlation spectroscopy, for studying atomic diffusion.

The principal question to be solved was whether it is feasible to bypass the need for macroscopic single crystals to be used as samples. It therefore deals with the possibility of obtaining single crystalline foils by repeated rolling and annealing, or, on the other hand, with the interpretation of XPCS correlation times obtained from polycrystalline foils. It is available here.

Monte-Carlo simulation of two-dimensional grain growth

This is the bachelor's thesis of Christian Schmid, submitted in July 2011. It is a simulation of the coarsening of grains in two dimensions, where the dynamics are not deterministic as in most other works, but given by a Monte Carlo-type stochastic process.

The results show that this is indeed a viable approach, although a correct implementation of the topological transitions of the grain boundary net has proven harder than thought before. Nevertheless, it allowed to generate nice movies! It is available here.
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