Testard Vincent, Berthier Ludovic, Kob Walter
Laboratoire Charles Coulomb, UMR 5221 CNRS and Université Montpellier 2, 34095 Montpellier, France.
J Chem Phys. 2014 Apr 28;140(16):164502. doi: 10.1063/1.4871624.
We use large-scale molecular dynamics simulations of a simple glass-forming system to investigate how its liquid-gas phase separation kinetics depends on temperature. A shallow quench leads to a fully demixed liquid-gas system whereas a deep quench makes the dense phase undergo a glass transition and become an amorphous solid. This glass has a gel-like bicontinuous structure that evolves very slowly with time and becomes fully arrested in the limit where thermal fluctuations become negligible. We show that the phase separation kinetics changes qualitatively with temperature, the microscopic dynamics evolving from a surface tension-driven diffusive motion at high temperature to a strongly intermittent, heterogeneous, and thermally activated dynamics at low temperature, with a logarithmically slow growth of the typical domain size. These results elucidate the microscopic mechanisms underlying a specific class of viscoelastic phase separation.
我们使用一个简单的玻璃形成系统的大规模分子动力学模拟来研究其液-气相分离动力学如何依赖于温度。浅淬火导致完全混合的液-气系统，而深淬火使致密相经历玻璃化转变并变成非晶态固体。这种玻璃具有类似凝胶的双连续结构，其随时间演化非常缓慢，并在热涨落可忽略不计的极限情况下完全停止。我们表明，相分离动力学随温度发生定性变化，微观动力学从高温下由表面张力驱动的扩散运动演变为低温下强烈间歇、不均匀且热激活的动力学，典型畴尺寸呈对数缓慢增长。这些结果阐明了一类特定的粘弹性相分离背后的微观机制。
