Fast and slow crystal growth kinetics in glass-forming melts
Fast and slow crystal growth kinetics in glass-forming melts
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DOI：
10.1063/1.4880959
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发表时间：
2014-06-07
影响因子：
4.4
通讯作者：
Greer, A. L.
中科院分区：
文献类型：
--
作者：
Orava, J.;Greer, A. L.
公布的晶体生长速率的值进行比较过冷玻璃形成液体在平面晶体-液体界面进行全等冻结。为了比较的目的，纯金属被认为是玻璃形成系统，使用分子动力学模拟的数据。对于每个系统，生长速率在位于玻璃化转变温度T-g和熔化温度T-m之间的温度T-max处具有最大值U-max。分类建议，根据液体的不稳定性（特别是快速结晶的倾向）。高不稳定性系统显示出“快速”生长，其特征在于高U-max、低T-max/T-m和U与T/T-m的非常宽的峰。相比之下，显示“缓慢”生长的系统具有低Umax、高Tmax/T-m和U对T/T-m的尖峰。尽管在纯金属和二氧化硅中观察到的U-max的差异超过11个数量级，但所调查的玻璃形成系统的范围符合一个共同的模式，其中不稳定性随着降低的玻璃化转变温度（T-g/T-m）和液体的更高脆性而增加。一个单一的参数，T-g/T-m和脆性的线性组合，可以显示出良好的相关性与U-max。对于所有的系统，在Umax的增长耦合到液体中的原子/分子的迁移率。发现，在玻璃形成系统的多样性中，Tmax/T-g = 1.48 +/- 0.15。(C)2014 AIP Publishing LLC.
Published values of crystal growth rates are compared for supercooled glass-forming liquids undergoing congruent freezing at a planar crystal-liquid interface. For the purposes of comparison pure metals are considered to be glass-forming systems, using data from molecular-dynamics simulations. For each system, the growth rate has a maximum value U-max at a temperature T-max that lies between the glass-transition temperature T-g and the melting temperature T-m. A classification is suggested, based on the lability (specifically, the propensity for fast crystallization), of the liquid. High-lability systems show "fast" growth characterized by a high U-max, a low T-max/T-m, and a very broad peak in U vs. T/T-m. In contrast, systems showing "slow" growth have a low Umax, a high T-max/T-m, and a sharp peak in U vs. T/T-m. Despite the difference of more than 11 orders of magnitude in U-max seen in pure metals and in silica, the range of glass-forming systems surveyed fit into a common pattern in which the lability increases with lower reduced glass-transition temperature (T-g/T-m) and higher fragility of the liquid. A single parameter, a linear combination of T-g/T-m and fragility, can show a good correlation with U-max. For all the systems, growth at Umax is coupled to the atomic/molecular mobility in the liquid. It is found that, across the diversity of glass-forming systems, T-max/T-g = 1.48 +/- 0.15. (C) 2014 AIP Publishing LLC.