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Regensburg 2019 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 36: Liquid and Amorphous Metals

MM 36.4: Talk

Thursday, April 4, 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 cp. However, density and local structure at the FST appear to change only continuously. Because of the peak in the cp, 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 (Zr0.606Cu0.29Al0.104), in contrast to the expectations for a phase transformation, we observed that the larger the system the smaller the peak in cp. 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.

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