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Master Kodanda Mangipudi, Astrid Pundt Finite element modelling of ordered hydride morphologies in thin Gd-films

The study of metal-hydrogen (M-H) systems is of great technological importance as they are identified as promising materials for renewable energy storage. To achieve high efficiency and safety in applications, it is crucial to understand the formation and growth of these metal hydrides.

Hydride formation and growth in nanoscale thin films has recently been studied by in-situ Scanning Tunneling Microscopy (UHV-STM) on thin and atomically flat epitaxial Gadolinium (Gd) films. Because of local volume expansion, hydrides become visible at the film surface and their formation and growth can be nicely studied. The results show surprising features like the formation of tiny islands that line up with characteristic size and spacing. Zig-zag as well as linear patterns are detected in the experiments (Fig.1). The aim of this theoretical project is to unravel the origin for this phenomenon.

Finite Element Method is a powerful tool to study the physics behind such arrangements in complex morphological surroundings. Using the commercial simulation software COMSOL, the specific conditions influencing the hydrides, such as the film thickness, lattice orientation, mechanical constraint due to the thick substrate, growth terraces, etc., can be addressed. COMSOL is a widely used simulation software both in academia and in industry to solve wide range of multiphysics problems. This project offers to gain a deep understanding of Finite Element Simulations, and may include modifications of the present tools.

We conduct this study in close collaboration with the experimental STM-group of Prof. Mathias Getzlaff, Institut für Angewandte Physik / Nanotechnologie at Düsseldorf University. Even new experiments can be designed based on the outcome of the FEM-simulations. This tight link to the experiments includes intensive discussion/visits of the research group in Düsseldorf during the project. Fig.: