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Five-fold symmetry as indicator of dynamic arrest in metallic glass-forming liquids.

Hu YC, Li FX, Li MZ, Bai HY, Wang WH - Nat Commun (2015)

Bottom Line: Because of the intricate atomic structure and dynamic behaviours of liquid, it is yet difficult to capture the underlying structural mechanism responsible for the marked slowing down during glass transition, which impedes deep understanding of the formation and nature of glasses.Here, we report that a universal structural indicator, the average degree of five-fold local symmetry, can well describe the slowdown dynamics during glass transition.A straightforward relationship between structural parameter and viscosity (or α-relaxation time) is introduced to connect the dynamic arrest and the underlying structural evolution.

View Article: PubMed Central - PubMed

Affiliation: Institute of Physics, Chinese Academy of Sciences, Beijing 100190 China.

ABSTRACT
With sufficient high cooling rates, a variety of liquids, including metallic melts, will cross a glass transition temperature and solidify into glass accompanying a marked increase of the shear viscosity in approximately 17 orders of magnitude. Because of the intricate atomic structure and dynamic behaviours of liquid, it is yet difficult to capture the underlying structural mechanism responsible for the marked slowing down during glass transition, which impedes deep understanding of the formation and nature of glasses. Here, we report that a universal structural indicator, the average degree of five-fold local symmetry, can well describe the slowdown dynamics during glass transition. A straightforward relationship between structural parameter and viscosity (or α-relaxation time) is introduced to connect the dynamic arrest and the underlying structural evolution. This finding would be helpful in understanding the long-standing challenges of glass transition mechanism in the structural perspective.

No MeSH data available.


Related in: MedlinePlus

The temperature dependence of the average cluster size.(a) The average cluster size formed by atoms with different thresholds of W in Cu46Zr46Al8 metallic glass-forming liquid, showing only the selection of 0.6 is reasonable. The inverse tendency of average cluster size for f5≥0.6 and f5≤0.2 indicates the existing competition between the incompatible symmetry during glass transition. (b) The evolution of the average cluster size with decreasing temperature in different systems. Temperature was scaled by Tg. Above Tg, the average cluster size increases remarkably while levels off after glass transition corresponding to the frozen structure in the glassy state.
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f6: The temperature dependence of the average cluster size.(a) The average cluster size formed by atoms with different thresholds of W in Cu46Zr46Al8 metallic glass-forming liquid, showing only the selection of 0.6 is reasonable. The inverse tendency of average cluster size for f5≥0.6 and f5≤0.2 indicates the existing competition between the incompatible symmetry during glass transition. (b) The evolution of the average cluster size with decreasing temperature in different systems. Temperature was scaled by Tg. Above Tg, the average cluster size increases remarkably while levels off after glass transition corresponding to the frozen structure in the glassy state.

Mentions: To unravel the spatial structure correlation, cluster analysis was conducted to investigate the cluster size evolution with temperature decreasing for different threshold of five-fold local symmetry40. A cluster can be defined if atoms with the same threshold are nearest neighbours, and the cluster size is defined as the number of contained atoms. Thus, the average cluster size was calculated according to , where n is the individual cluster size and P(n) is its probability40. The thresholds of f5≥0.5, 0.6 and 0.7 were chosen for cluster analysis. The threshold of f5≤0.2 was also tested for a comparison. As shown in Fig. 6a, the average cluster size is increasing for the threshold of f5≥0.5, 0.6 and 0.7, respectively, during quenching, whereas the average cluster size of f5≤0.2 is decreasing. This indicates that the population of the Voronoi clusters with higher degree of five-fold local symmetry is increasing with decreasing temperature and form larger and larger clusters, whereas the population of the Voronoi clusters with lower degree of five-fold local symmetry decreases.


Five-fold symmetry as indicator of dynamic arrest in metallic glass-forming liquids.

Hu YC, Li FX, Li MZ, Bai HY, Wang WH - Nat Commun (2015)

The temperature dependence of the average cluster size.(a) The average cluster size formed by atoms with different thresholds of W in Cu46Zr46Al8 metallic glass-forming liquid, showing only the selection of 0.6 is reasonable. The inverse tendency of average cluster size for f5≥0.6 and f5≤0.2 indicates the existing competition between the incompatible symmetry during glass transition. (b) The evolution of the average cluster size with decreasing temperature in different systems. Temperature was scaled by Tg. Above Tg, the average cluster size increases remarkably while levels off after glass transition corresponding to the frozen structure in the glassy state.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4595736&req=5

f6: The temperature dependence of the average cluster size.(a) The average cluster size formed by atoms with different thresholds of W in Cu46Zr46Al8 metallic glass-forming liquid, showing only the selection of 0.6 is reasonable. The inverse tendency of average cluster size for f5≥0.6 and f5≤0.2 indicates the existing competition between the incompatible symmetry during glass transition. (b) The evolution of the average cluster size with decreasing temperature in different systems. Temperature was scaled by Tg. Above Tg, the average cluster size increases remarkably while levels off after glass transition corresponding to the frozen structure in the glassy state.
Mentions: To unravel the spatial structure correlation, cluster analysis was conducted to investigate the cluster size evolution with temperature decreasing for different threshold of five-fold local symmetry40. A cluster can be defined if atoms with the same threshold are nearest neighbours, and the cluster size is defined as the number of contained atoms. Thus, the average cluster size was calculated according to , where n is the individual cluster size and P(n) is its probability40. The thresholds of f5≥0.5, 0.6 and 0.7 were chosen for cluster analysis. The threshold of f5≤0.2 was also tested for a comparison. As shown in Fig. 6a, the average cluster size is increasing for the threshold of f5≥0.5, 0.6 and 0.7, respectively, during quenching, whereas the average cluster size of f5≤0.2 is decreasing. This indicates that the population of the Voronoi clusters with higher degree of five-fold local symmetry is increasing with decreasing temperature and form larger and larger clusters, whereas the population of the Voronoi clusters with lower degree of five-fold local symmetry decreases.

Bottom Line: Because of the intricate atomic structure and dynamic behaviours of liquid, it is yet difficult to capture the underlying structural mechanism responsible for the marked slowing down during glass transition, which impedes deep understanding of the formation and nature of glasses.Here, we report that a universal structural indicator, the average degree of five-fold local symmetry, can well describe the slowdown dynamics during glass transition.A straightforward relationship between structural parameter and viscosity (or α-relaxation time) is introduced to connect the dynamic arrest and the underlying structural evolution.

View Article: PubMed Central - PubMed

Affiliation: Institute of Physics, Chinese Academy of Sciences, Beijing 100190 China.

ABSTRACT
With sufficient high cooling rates, a variety of liquids, including metallic melts, will cross a glass transition temperature and solidify into glass accompanying a marked increase of the shear viscosity in approximately 17 orders of magnitude. Because of the intricate atomic structure and dynamic behaviours of liquid, it is yet difficult to capture the underlying structural mechanism responsible for the marked slowing down during glass transition, which impedes deep understanding of the formation and nature of glasses. Here, we report that a universal structural indicator, the average degree of five-fold local symmetry, can well describe the slowdown dynamics during glass transition. A straightforward relationship between structural parameter and viscosity (or α-relaxation time) is introduced to connect the dynamic arrest and the underlying structural evolution. This finding would be helpful in understanding the long-standing challenges of glass transition mechanism in the structural perspective.

No MeSH data available.


Related in: MedlinePlus