Onset of Cooperative Dynamics in an Equilibrium Glass-Forming Metallic Liquid

Abstract

Onset of cooperative dynamics has been observed in many molecular liquids, colloids, and granular materials in the metastable regime on approaching their respective glass or jamming transition points, and is considered to play a significant role in the emergence of the slow dynamics. However, the nature of such dynamical cooperativity remains elusive in multicomponent metallic liquids characterized by complex many-body interactions and high mixing entropy. Herein, we report evidence of onset of cooperative dynamics in an equilibrium glass-forming metallic liquid (LM601: Zr51Cu36Ni4Al9). This is revealed by deviation of the mean effective diffusion coefficient from its high-temperature Arrhenius behavior below TA ≈ 1300 K, i.e., a crossover from uncorrelated dynamics above TA to landscape-influenced correlated dynamics below TA. Furthermore, the onset/crossover temperature TA in such a multicomponent bulk metallic glass-forming liquid is observed at approximately twice of its calorimetric glass transition temperature (Tg ≈ 697 K) and in its stable liquid phase, unlike many molecular liquids.

Correlation between Fragility and the Arrhenius Crossover Phenomenon in Metallic, Molecular, and Network Liquids

“…Three distinct behaviors can be identified: 1) For metallic liquids, it is remarkable that all data points follow a straight line with a slope of 2. In our previous QENS experiments, we have made a similar observation of T A ≈ 2 T g for diffusion in LM601 [13,27].…”

“…1 shows that all of the 11 glass-forming metallic melts exhibit a clear deviation from their high-temperature Arrhenius behaviors. It should be noted that relaxation in such metallic liquids are slightly stretched even in the very high temperature liquid state due to differences between the mobilities of constituent elements [27]. Nevertheless, previous studies has shown T A to be the same for all components [26].…”

“…The onset of cooperative dynamics has been previously characterized in fragile liquids by studying the deviation of transport coefficients from their high-temperature Arrhenius behavior [9,10,13,26]. Herein, we compile diffusion coefficient data of 11 metallic liquids [27][28][29][30][31][32][33][34][35][36][37][38] measured using Quasi-Elastic Neutron Scattering (QENS) that measures the mean relaxation dynamics of multicomponent metallic liquids. Fig.…”

Computational modeling sheds light on structural evolution in metallic glasses and supercooled liquids

“…It is worth noting that in addition to monitoring structural ordering upon cooling to temperatures close to T g as discussed above, significant progress has been made very recently to understand the dynamical crossover of transport properties from Arrhenius to super-Arrhenius behavior, at high temperatures in liquids that are close to equilibrium (the crossover temperature is at~2T g for metallic liquids). 32,[78][79][80][81][82] In this regime, atomic correlations responsible for the onset of cooperative dynamics are being analyzed to provide a structural origin of the cross-over as well as a new perspective of the liquid fragility.…”

Direct observation of dynamic crossover in fragile molecular glass formers with 2D IR vibrational echo spectroscopy

“…α-relaxation, is at least as important as T c in describing glassy phenomena. [21][22][23][24] In terms of the potential energy landscape description of the glass transition, 21,22,25 above T o , the liquid is unaffected by the underlying landscape and behaves like a normal liquid. Below T o but above T c , the liquid first becomes "landscape influenced."…”