Fragility transition in GeSe2–Se liquids
Fragility transition in GeSe2–Se liquids
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DOI：
10.1039/b201396g
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发表时间：
2002-07
影响因子：
3.3
通讯作者：
S. Stølen;T. Grande;H. Johnsen
中科院分区：
文献类型：
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作者：
S. Stølen;T. Grande;H. Johnsen
本文报道了GeSe_2-Se体系液体的热容和熵。该系统的热力学进行评估和讨论，根据早期报道的液体GeSe 2的粘度和最近的结构研究。液体GeSe 2的热力学表明，广泛的结构无序发生在液体中的加热，并指向一个脆弱的熔体在高温下，而接近玻璃化转变温度的系统的热力学特性表明一个脆弱得多的字符。从早期的粘度数据中可以明显看出一个一致的图像; GeSe 2-Se玻璃的粘度刚好高于Tg，在x = 0.225附近支持脆性最小值，（x是GexSe 1 −x中的x），而从稳定液体和非粘性区域的粘度中可以明显看出脆性单调增加。我们建议，上述差异之间的熔体接近Tg的行为，并在高温下可以解释由一个脆弱的强过渡过冷GeSe 2-Se。该过渡与GeSe 2的化学无序和密度最小值的发生有关。其他四面体液体的脆到强转变也与一级液-液转变有关，最近也讨论了GeSe 2。
The heat capacity and entropy of liquids in the GeSe2–Se system are reported. The thermodynamics of the system is evaluated and discussed in light of earlier reported viscosities and recent structural studies of liquid GeSe2. The thermodynamics of liquid GeSe2 suggest that extensive structural disordering takes place in the liquid on heating and points to a fragile melt at high temperatures whereas the thermodynamic characteristics of the system close to the glass transition temperature suggests a much less fragile character. A consistent picture is evident from earlier viscosity data; the viscosity of GeSe2–Se glasses just above Tg supports a fragility minimum near x = 0.225, (x is x in GexSe1−x) while a monotonically increasing fragility is evident from the viscosity in the stable liquid and non-viscous region. We propose that the above discrepancy between the behaviour of the melts close to Tg and at high temperatures can be explained by a fragile-to-strong transition in supercooled GeSe2–Se. The transition is related to the onset of chemical disorder and the density minimum of GeSe2. The proposed fragile-to-strong transition of other tetrahedral liquids has also been linked to a first order liquid–liquid transition, which recently also have been discussed for GeSe2.