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MM: Fachverband Metall- und Materialphysik

MM 36: Liquid and Amorphous Metals

MM 36.4: Vortrag

Donnerstag, 4. April 2019, 11:00–11:15, H46

Quasi-discontinuous change of the density correlation length at the fragile-to-strong transition in a bulk-metallic-glass forming melt — •Sergey V. Sukhomlinov and Martin H. Mueser — Universität des Saarlandes, 66123 Saarbrücken, Germany

Many bulk-metallic-glass (BMG) forming melts undergo a fragile-to-strong transition (FST), which is accompanied by a small but noticeable peak in the specific heat c_p. However, density and local structure at the FST appear to change only continuously. Because of the peak in the c_p, the FST is sometimes interpreted as a smeared-out phase transition. This motivated us to study how the specific heat, dynamical and structural properties of a selected BMG depend near the FST temperature on the system size using computer simulations.

For a ternary BMG former (Zr_0.606Cu_0.29Al_0.104), in contrast to the expectations for a phase transformation, we observed that the larger the system the smaller the peak in c_p. This result, along with size dependence of other properties, is difficult to reconcile with the interpretation of the FST being a (smeared-out) phase transformation.

The results from structural analysis showed a smooth evolution of radial distribution functions (RDF) at small distances through the FST. However, the long-range density correlation length increases (quasi-) discontinuously at the FST as revealed by an Ornstein-Zernike-based analysis of the RDF. Likewise, the temperature derivative of the Zr-Zr mean nearest-neighbor distance decreases (quasi-) discontinuously at the FST. These observations add to the rich phenomenology of FSTs lacking a theoretical understanding.