Regensburg 2013 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 16: Theory: Metal-insulator transitions / Electronic structure calculations

HL 16.5: Talk

Monday, March 11, 2013, 16:30–16:45, H13

Ab initio simulation of crystallization in phase change materials — •Ider Ronneberger¹, Yan Li¹, Wei Zhang¹, Sebastiano Caravati², Eshet Hagai², Michele Parrinello², and Riccardo Mazzarello¹ — ¹Institut für Theoretische Physik, RWTH Aachen — ²Comp. Science, Dep. of Chem. and Appl. Biosciences, ETH Zürich

The microscopic understanding of the crystallization processes in the technologically relevant phase change materials (PCM) is desirable, in that it could eventually lead to improved properties for applications. Ab initio Molecular Dynamics (AIMD) simulations are very useful to investigate these processes and plenty of atomistic studies were conducted in the field of PCM research. However typical simulation times of AIMD are of the order of 1 ns or less, so that observation of long-time processes and rare events (such as crystallization at low temperature) is computationally not affordable. A new efficient sampling method, called metadynamics, was introduced a decade ago, which can accelerate the dynamics by biasing with history-dependent potentials and lead to an estimation of the free energy change during the process. In this study we employed the so called Well-Tempered version of metadynamics in combination with AIMD to study the crystallization of GeTe as a model representative of PCMs. Using a few selected reaction coordinates, models with up to 512 atoms were considered and the free energy change upon crystallization computed at 600 K. The results show that this method is a promising tool to determine nucleation barriers in PCMs. We plan to extend this study to different temperature ranges and other PCMs.