Laboratoire Charles Coulomb (L2C), Université de Montpellier, CNRS, Montpellier 34095, France.
Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, United Kingdom.
Proc Natl Acad Sci U S A. 2023 Apr 18;120(16):e2220824120. doi: 10.1073/pnas.2220824120. Epub 2023 Apr 11.
The discovery of ultrastable glasses raises novel challenges about glassy systems. Recent experiments studied the macroscopic devitrification of ultrastable glasses into liquids upon heating but lacked microscopic resolution. We use molecular dynamics simulations to analyze the kinetics of this transformation. In the most stable systems, devitrification occurs after a very large time, but the liquid emerges in two steps. At short times, we observe the rare nucleation and slow growth of isolated droplets containing a liquid maintained under pressure by the rigidity of the surrounding glass. At large times, pressure is released after the droplets coalesce into large domains, which accelerates devitrification. This two-step process produces pronounced deviations from the classical Avrami kinetics and explains the emergence of a giant lengthscale characterizing the devitrification of bulk ultrastable glasses. Our study elucidates the nonequilibrium kinetics of glasses following a large temperature jump, which differs from both equilibrium relaxation and aging dynamics, and will guide future experimental studies.
超稳玻璃的发现给玻璃态系统带来了新的挑战。最近的实验研究了超稳玻璃在加热时宏观上向液体的非晶质转化，但缺乏微观分辨率。我们使用分子动力学模拟来分析这种转变的动力学。在最稳定的系统中，玻璃化转变发生在非常长的时间之后，但液体是分两步出现的。在短时间内，我们观察到很少有孤立液滴的成核和缓慢生长，这些液滴中的液体在周围玻璃的刚性下保持压力。在长时间后，液滴合并成大的区域后会释放压力，这会加速玻璃化转变。这种两步过程产生了与经典 Avrami 动力学明显的偏离，并解释了大块超稳玻璃玻璃化转变出现的巨大长度尺度。我们的研究阐明了在经历大的温度跳跃后的玻璃的非平衡动力学，这与平衡弛豫和老化动力学不同，并将指导未来的实验研究。
