Dresden 2014 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 26: Focus Session: Slow Dynamics in Glasses and Granular Matter I (joint session DY/ CPP/ DF)

DY 26.5: Vortrag

Donnerstag, 3. April 2014, 11:15–11:30, HÜL 186

Vibrational Masking of Critical Decay in the Early beta-Relaxation Regime of Incoherent Intermediate Scattering Functions in Simulated Glass Forming Ni0.5Zr0.5 — •Helmar Teichler — Institut f. Materialphysik, Univ. Göttingen

Results are presented concerning the origin of discrepancy between mode coupling theory (MCT) prediction for critical decay in the early beta-regime and molecular dynamics (MD) simulation data. The discrepancy is known since long in the literature and is heuristically ascribed to effects of atomic vibrations not fully taken into account in MCT. A proper theoretical treatment is missing so far. Here I present a formally exact framework for analyzing the MD data, which allows deducing the origin of the discrepancy and its quantitative description, and I apply it to MD simulated glass forming Ni0.5Zr0.5. The approach relates incoherent intermediate scattering functions (ISFs) from atomic trajectories, which show the discrepancy, to those from inherent structure (IS), which are in agreement with MCT. Cumulant expansion of the ISFs demonstrates that the discrepancy reflects the vibrational density of states, with minor effect of the Boson peak. The results for Ni0.5Zr0.5 rely on the fact that there are only weak correlations between atomic vibrations and IS relaxation displacements in the beta-regime, and that the essential part of the vibrational displacements distribution acts Gaussian-like.