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DY: Fachverband Dynamik und Statistische Physik

DY 13: Glass I (joint session with DF)

DY 13.3: Vortrag

Dienstag, 27. März 2007, 10:30–10:45, H23

Microscopic mechanism of the β-process in metallic glass formers: molecular dynamics results for NiZr — •Helmar Teichler — Inst. f. Materials Physics, University of Göttingen

For glass formers around and below the dynamical critical temperature Tc of mode coupling theory (MCT), the fluctuation spectrum shows the β-regime in the time domain as precursor of the final α-decay. Recently, the β-regime has re-attracted much interest due to observation of the β-excess wing in spectroscopic data of a metallic glass by Rösner, Samwer, and Lunkenheimer (Europhys. Lett. 92, 105701(2004)) and the evaluation of the interconnection between Cole-Cole peak and spectral properties of the β-regime in the MCT by Sperl (PRE, 74, 011503(2006)). Here we address the question of the microscopic mechanisms that take place in the corresponding frequency regime in metallic glasses. Regarding this, molecular dynamics simulation data of vitrifying Ni0.5Zr0.5 melts are investigated by studying their inherent structure dynamics in order to eliminate the masking, predominant effect of thermal single-particle vibrations. Analysis of the remaining dynamics by nearest neighbour correlation functions, aimed at identifying topological fluctuations of the system, yields reversible over-barrier transitions of correlated chains of atoms as source of a β-peak between single-particle vibrations and the α-decay.