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TT: Fachverband Tiefe Temperaturen
TT 32: Focused Session: Frontiers of Electronic Structure Theory 3 (jointly with HL and O)
TT 32.4: Vortrag
Dienstag, 12. März 2013, 11:30–11:45, H36
Density functional / molecular dynamics simulations of nucleus-driven crystallization of amorphous Ge2Sb2Te5 — •Jaakko Akola1,2,3, Janne Kalikka4, Julen Larrucea4, and Robert O. Jones3 — 1Department of Physics, Tampere University of Technology, Finland — 2COMP Centre of Excellence, Department of Applied Physics, Aalto University, Finland — 3GRSS and PGI-1, Forschungszentrum Jülich, Germany — 4Nanoscience Center, Department of Physics, University of Jyväskylä, Finland
Early stages of nucleus-driven crystallization of the prototype phase change material Ge2Sb2Te5 have been studied by massively-parallel density functional/molecular dynamics simulations for amorphous samples (460 and 648 atoms) at 500, 600, and 700 K [1]. All systems assumed a fixed cubic seed of 58 atoms and 6 vacancies in order to achieve sub-nanosecond phase transition. Crystallization occurs within 600 ps for the 460-atom system at 600 and 700 K, and signs of crystallization (nucleus growth, percolation) are present in the others. Crystallization is accompanied by an increase in the number of ABAB squares (A: Ge, Sb, B: Te) [2,3], and atoms of all elements move significantly. The evolution of cavities/vacancies is closely monitored. The existence of Te-Te, Ge-Ge, Ge-Sb, and Sb-Sb (wrong) bonds is an inevitable consequence of rapid crystallization.
[1] J. Kalikka, J. Akola, J. Larrucea, and R. O. Jones, Physical Review B 86, 144113 (2012). [2] J. Akola and R. O. Jones, Phys. Rev. B 76, 235201 (2007). [3] J. Akola and R. O. Jones, Phys. Rev. Lett. 100, 205502 (2008).