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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

Relation between structure parameter W and α-relaxation time τα.The dotted and solid curves are simulation data and the fittings with equation (5), respectively.
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f3: Relation between structure parameter W and α-relaxation time τα.The dotted and solid curves are simulation data and the fittings with equation (5), respectively.

Mentions: where τ0 is the relaxation time at infinite liquidus temperature, and δ and D are fitting parameters. Figure 3 illustrates the α-relaxation time τα as a function of W and the fittings of equation (5) for various MG-forming liquids (R2≥0.99 for all the fittings). Remarkably, equation (5) can well describe the relationship between structural relaxation time and the five-fold local symmetry in MG-forming liquids. In addition, δ is fitted to be about 6.78, 11.52, 13.58, 17.65, 17.95, 18.92, 18.94, and 32.74 for Cu46Zr46Al8, Zr45Cu45Ag10, Cu50Zr50, Ni80P20, Pd82Si18, Mg65Cu25Y10, Ni33Zr67 and Ni50Al50 MG-forming liquids, respectively. Clearly, δ is quite different for different systems, whereas the fitting parameter D is found to be similar (∼10−5) in different systems. As mentioned above, δ reflects the sensitivity of the viscosity or α-relaxation time to structure change. Therefore, the effect of the structure change on the relaxation dynamics is significantly different in different MG-forming liquids. Our results show that there exists a universal underlying structural evolution in MG-forming liquids, which is responsible for the marked dynamic slowdown. The results are also in agreement with the observation of locally favoured structure in colloidal gels during gelation12 and granular systems13, and medium-range crystalline order in granular liquids during liquid–glass transition35.


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)

Relation between structure parameter W and α-relaxation time τα.The dotted and solid curves are simulation data and the fittings with equation (5), respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f3: Relation between structure parameter W and α-relaxation time τα.The dotted and solid curves are simulation data and the fittings with equation (5), respectively.
Mentions: where τ0 is the relaxation time at infinite liquidus temperature, and δ and D are fitting parameters. Figure 3 illustrates the α-relaxation time τα as a function of W and the fittings of equation (5) for various MG-forming liquids (R2≥0.99 for all the fittings). Remarkably, equation (5) can well describe the relationship between structural relaxation time and the five-fold local symmetry in MG-forming liquids. In addition, δ is fitted to be about 6.78, 11.52, 13.58, 17.65, 17.95, 18.92, 18.94, and 32.74 for Cu46Zr46Al8, Zr45Cu45Ag10, Cu50Zr50, Ni80P20, Pd82Si18, Mg65Cu25Y10, Ni33Zr67 and Ni50Al50 MG-forming liquids, respectively. Clearly, δ is quite different for different systems, whereas the fitting parameter D is found to be similar (∼10−5) in different systems. As mentioned above, δ reflects the sensitivity of the viscosity or α-relaxation time to structure change. Therefore, the effect of the structure change on the relaxation dynamics is significantly different in different MG-forming liquids. Our results show that there exists a universal underlying structural evolution in MG-forming liquids, which is responsible for the marked dynamic slowdown. The results are also in agreement with the observation of locally favoured structure in colloidal gels during gelation12 and granular systems13, and medium-range crystalline order in granular liquids during liquid–glass transition35.

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