60 research outputs found
Microscopic evidence of the connection between liquid-liquid transition and dynamical crossover in an ultraviscous metallic glass former
Liquid-liquid transitions are interesting to many researchers since they occur in systems as diverse as monoatomic liquids, multicomponent oxides, and metallic glass formers. In some cases, the crossover is accompanied by changes in the dynamical properties. By combining state-of-the-art synchrotron techniques, we followed the structure and atomic motion during quasistatic cooling of the Au49Cu26.9Si16.3Ag5.5Pd2.3 metallic glass former from the low-temperature supercooled liquid. With this thermal protocol, we were able to lower the glass transition temperature far enough to reveal a liquid-liquid crossover between two amorphous structures corresponding to two ultraviscous liquids with different kinetic behavior. This transition is in competition with vitrification, which occurs at conventional cooling rates, and is accompanied by structural changes not affecting the average density. Our results provide a direct connection between polyamorphism and dynamical crossover, and an alternative case to add to the highly debated topic on the low-temperature divergence of the dynamics in supercooled liquids.Peer ReviewedPostprint (published version
Disentangling structural and kinetic components of the {\alpha}-relaxation in supercooled metallic liquids
The particle motion associated to the {\alpha}-relaxation in supercooled
liquids is still challenging scientists due to its difficulty to be probed
experimentally. By combining synchrotron techniques, we found the existence of
microscopic structure-dynamics relationships in Pt42.5Cu27Ni9.5P21 and
Pd42.5Cu27Ni9.5P21 liquids which allows us to disentangle structural and
kinetic contributions to the {\alpha}-process. While the two alloys show
similar kinetic fragilities, their structural fragilities differ and correlate
with the temperature dependence of the stretching parameter describing the
decay of the density fluctuations. This implies that the evolution of dynamical
heterogeneities in supercooled alloys is determined by the rigidity of the melt
structure. We find also that the atomic motion not only reflects the
topological order but also the chemical short-range order, which can lead to a
surprising slowdown of the {\alpha}-process at the mesoscopic length scale.
These results will contribute to the comprehension of the glass transition,
which is still missing
Disentangling structural and kinetic components of the α-relaxation in supercooled metallic liquids
The particle motion associated to the α-relaxation in supercooled liquids is still challenging
scientists due to its difficulty to be probed experimentally. By combining synchrotron techniques, we report the existence of microscopic structure-dynamics relationships in
Pt42.5Cu27Ni9.5P21 and Pd42.5Cu27Ni9.5P21 liquids which allows us to disentangle structural and
kinetic contributions to the α-process. While the two alloys show similar kinetic fragilities,
their structural fragilities differ and correlate with the temperature dependence of the
stretching parameter describing the decay of the density fluctuations. This implies that the
evolution of dynamical heterogeneities in supercooled alloys is determined by the rigidity of
the melt structure. We find also that the atomic motion not only reflects the topological order
but also the chemical short-range order, which can lead to a surprising slowdown of the αprocess at the mesoscopic length scale. These results will contribute to the comprehension of
the glass transition, which is still missing
Bernd Hontschik: 'Körper, Seele, Mensch. Versuch über die Kunst des Heilens. Frankfurt am Main (Suhrkamp) 2006
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