Atomistic simulations of the crystallization of amorphous GeTe nanoparticles|分子动力学模拟数据集|相变材料数据集

The effect of dimensionality reduction on the crystallization kinetics of phase change materials is of relevance for the operation of ultrascaled memory devices. Therefore, the crystallization of amorphous nanoparticles (NPs) of the prototypical phase change compounds, GeTe and Ge₂Sb₂Te₅, has been addressed by several experimental works in recent years. In this work, we performed molecular dynamics simulations of the crystallization process of amorphous GeTe NPs with diameter in the range 3-6 nm (512-4096 atoms) by exploiting a machine-learned interatomic potential. We saw a few crystal nucleation events in the larger NPs but no crystallization in the smallest NP, 3 nm in diameter, in simulations lasting up to 80 ns in the temperature range 500-750 K. The analysis of the crystallization kinetics suggests that the nucleation rate per volume decreases with the NP size to an extent that prevents us from seeing crystallization in the smallest NP on our simulation time scale. This result is consistent with the large raise in crystallization temperature observed experimentally for NPs with diameters shorter than 3.5 nm.

对相变材料结晶动力学中维度缩减效应的研究，对于超缩放存储设备的工作具有重要意义。因此，近年来，通过多种实验研究已对典型相变化合物锗碲（GeTe）和锗锑锑碲（Ge₂Sb₂Te₅）的无定形纳米颗粒（NPs）的结晶过程进行了探讨。在本研究中，我们利用机器学习得到的原子间势能，对直径在3-6 nm（原子数512-4096）范围内的无定形锗碲NPs的结晶过程进行了分子动力学模拟。我们在较大的NPs中观察到了几个晶体成核事件，但在直径最小的NPs（3 nm）中，在持续80 ns、温度范围为500-750 K的模拟中，并未观察到结晶现象。对结晶动力学的分析表明，单位体积内的成核率随着NPs尺寸的减小而降低，以至于在我们的模拟时间尺度上无法观察到最小NPs的结晶。这一结果与实验观察到的直径小于3.5 nm的NPs结晶温度显著升高的现象相一致。