Phase-change materials (PCMs) are finding wide applications in emerging technologies such as nonvolatile phase-change random-access memory and in-memory computing devices by utilising the ultrafast and reversible amorphous-to-crystal transition. The crystallisation of the amorphous state is much slower compared to the crystal melting, hence representing a bottleneck in the further development of new technologies. Here, we disclose the detailed crystallisation pathway of amorphous Ge₂Sb₂Te₅ (GST) via ab initio molecular dynamics simulations. By probing the local order with a highly sensitive metric, we detect the formation of a sub-critical nucleus formed by the spontaneous aggregation of highly ordered octahedral-like atoms. Specifically, we observe that Sb atoms recover octahedral-like geometry quicker than Ge atoms, implying that the different mobility of different species plays a central role in the overall process. With respect to other less locally-ordered (hence transient) domains, this stable precursor is characterised by lower energy, is resilient to melting, and acts as a skeleton over which the critical nucleus further develops. The detailed understanding of the kinetics of homogeneous nucleation in GST opens the doorway for the development of more efficient PCM-based storage devices by a rational composition design and, ultimately, for the boosting of the speed and efficiency of computing architectures.

相变材料 (PCM) 通过利用超快和可逆的非晶到晶体转变在非易失性相变随机存取存储器和内存计算设备等新兴技术中得到广泛应用。与晶体熔化相比，非晶态的结晶要慢得多，因此是新技术进一步发展的瓶颈。在这里，我们通过ab公开了无定形 Ge ₂ Sb ₂ Te ₅ (GST)的详细结晶途径初始分子动力学模拟。通过用高度敏感的度量探测局部顺序，我们检测到由高度有序的八面体状原子的自发聚集形成的亚临界核的形成。具体而言，我们观察到 Sb 原子比 Ge 原子更快地恢复八面体几何形状，这意味着不同物种的不同迁移率在整个过程中起着核心作用。相对于其他不那么局部有序（因此是瞬态）的域，这种稳定的前驱体的特点是能量较低，对熔化有弹性，并充当临界核进一步发展的骨架。对 GST 中均相成核动力学的详细理解为通过合理的成分设计开发更高效的基于 PCM 的存储设备打开了大门，最终，