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DS: Fachverband Dünne Schichten

DS 3: Phase Change / Resistive Switching

DS 3.13: Talk

Monday, March 7, 2016, 12:45–13:00, H8

Ab initio Simulations of Liquid Phase-Change Materials — •Mathias Schumacher¹, Hans Weber^2,3, Ivan Kaban^2,3, Riccardo Mazzarello^1,4, and Pal Jovari⁵ — ¹Institute for Theoretical Solid State Physics, RWTH Aachen University, Germany — ²IFW Dresden, Institute for Complex Materials, Dresden, Germany — ³Institute of Materials Science, TU Dresden, Germany — ⁴JARA FIT and JARA HPC, RWTH Aachen, Germany — ⁵Department of Complex Fluids, Institute for Solid State Physics and Optics, Wigner RCP of the H.A.S., Hungary

Phase-Change materials (PCMs) undergo fast and reversible transitions between the amorphous and crystalline phase at high temperature. This property is exploited in non-volatile phase-change memories and rewritable optical disks. The liquid state plays a role in both directions of the switching process: the amorphization occurs upon rapid quenching from the liquid state, whereas fast crystallization takes place from the supercooled liquid. Hence, detailed knowledge of the properties of liquid PCMs is crucial for the understanding of the switching phenomenon. Here we present large scale ab initio molecular dynamics (AIMD) simulations of liquid and supercooled liquid PCMs. We consider large models of GeTe, Ge₂Sb₂Te₅ and Ag, In-doped Sb₂Te containing about 500-600 atoms and carry out long simulations (of the order of 100 ps) at different temperatures, below and above the melting temperature. We extract structural and dynamic properties from these trajectories, including radial and angle distribution functions and viscosities. The results are in fair agreement with recent experiments.