Limits...
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

Correlation matrix of atoms with diverse W.Correlation matrices of Cij between atoms classified into diverse W in (a) Cu46Zr46Al8 and (b) Mg65Cu25Y10 at T=1.2Tg (the behaviour of Cij is similar at different temperatures).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4595736&req=5

f5: Correlation matrix of atoms with diverse W.Correlation matrices of Cij between atoms classified into diverse W in (a) Cu46Zr46Al8 and (b) Mg65Cu25Y10 at T=1.2Tg (the behaviour of Cij is similar at different temperatures).

Mentions: To get deep insight into the correlation between W and dynamics, we analysed the spatial structures related to the different degree of five-fold local symmetry. Here a nearest-neighbour correlation index Cij defined as was adopted39, which reflects the spatial correlation between central atoms of polyhedra i and j, where Pij and represent the probability of polyhedra types i and j being the nearest neighbours in real structure model and in the case of the distributions of indices are spatially random, respectively. Positive values of Cij indicate strong correlation between polyhedra i and j and vice versa. Figure 5 shows the correlation matrix of Cij between atoms with classified W values at 1.2Tg for Cu46Zr46Al8 and Mg65Cu25Y10 MG-forming liquids, respectively (see Supplementary Fig. 6 for other systems). It is clearly seen that the correlation matrix of Cij exhibits similar patterns in various MG-forming liquids, although the structural motifs in these systems are different10. The correlation patterns are also similar at different temperatures (not shown). This indicates that the structural parameter W is generic in describing the structure properties and spatial structure correlations in MG-forming liquids. The values of Cij in the upper-left and bottom-right corners in the correlation maps are larger than 0, whereas those in the upper-right and bottom-left corners are smaller than 0. This implies that the atoms with f5≥0.6 or f5≤0.4 tend to form clusters, whereas the atoms with f5≥0.6 and f5≤0.4 tend to avoid each other.


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)

Correlation matrix of atoms with diverse W.Correlation matrices of Cij between atoms classified into diverse W in (a) Cu46Zr46Al8 and (b) Mg65Cu25Y10 at T=1.2Tg (the behaviour of Cij is similar at different temperatures).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f5: Correlation matrix of atoms with diverse W.Correlation matrices of Cij between atoms classified into diverse W in (a) Cu46Zr46Al8 and (b) Mg65Cu25Y10 at T=1.2Tg (the behaviour of Cij is similar at different temperatures).
Mentions: To get deep insight into the correlation between W and dynamics, we analysed the spatial structures related to the different degree of five-fold local symmetry. Here a nearest-neighbour correlation index Cij defined as was adopted39, which reflects the spatial correlation between central atoms of polyhedra i and j, where Pij and represent the probability of polyhedra types i and j being the nearest neighbours in real structure model and in the case of the distributions of indices are spatially random, respectively. Positive values of Cij indicate strong correlation between polyhedra i and j and vice versa. Figure 5 shows the correlation matrix of Cij between atoms with classified W values at 1.2Tg for Cu46Zr46Al8 and Mg65Cu25Y10 MG-forming liquids, respectively (see Supplementary Fig. 6 for other systems). It is clearly seen that the correlation matrix of Cij exhibits similar patterns in various MG-forming liquids, although the structural motifs in these systems are different10. The correlation patterns are also similar at different temperatures (not shown). This indicates that the structural parameter W is generic in describing the structure properties and spatial structure correlations in MG-forming liquids. The values of Cij in the upper-left and bottom-right corners in the correlation maps are larger than 0, whereas those in the upper-right and bottom-left corners are smaller than 0. This implies that the atoms with f5≥0.6 or f5≤0.4 tend to form clusters, whereas the atoms with f5≥0.6 and f5≤0.4 tend to avoid each other.

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