Konstantinou K, Mocanu F C, Lee T H, Elliott S R
Department of Chemistry, University of Cambridge, CB2 1EW Cambridge, United Kingdom.
J Phys Condens Matter. 2018 Nov 14;30(45):455401. doi: 10.1088/1361-648X/aae340.
Ion irradiation corresponds to a process that involves the production of non-equilibrium cascades in the host material, and the atomistic modelling of such events in glasses is challenging. Here, non-equilibrium cascades in amorphous GeSbTe phase-change memory material have been investigated by means of first-principles molecular-dynamics simulations. A stochastic boundary-conditions approach is employed to treat the thermal nature of the cascades and drive the modelled system back to equilibrium in a natural way, while four different initial thermal-spike energies are considered. A comprehensive analysis of the cascade evolution is presented with respect to the kinetic profile and the dynamics of the cascade inside the glass structure. The modelling results show that the instantaneous maximum kinetic energy decays rapidly with time, and that the time-scale of the ballistic phase of the cascade inside the glass model is very short. The quality of the implemented approach is validated through a comparison of the calculated structure factor for the modelled glasses with experimental data from the literature. Analysis of the bonding for all the species in the glass structure highlights particular structural modifications in the connectivity of the amorphous network due to the simulated cascade.
离子辐照对应于一个在主体材料中产生非平衡级联的过程，而对玻璃中此类事件进行原子尺度建模具有挑战性。在此，通过第一性原理分子动力学模拟研究了非晶态GeSbTe相变存储材料中的非平衡级联。采用随机边界条件方法来处理级联的热性质，并以自然的方式驱使建模系统回到平衡状态，同时考虑了四种不同的初始热尖峰能量。针对玻璃结构中级联的动力学轮廓和级联动力学，对级联演化进行了全面分析。建模结果表明，瞬时最大动能随时间迅速衰减，并且玻璃模型中级联弹道阶段的时间尺度非常短。通过将建模玻璃的计算结构因子与文献中的实验数据进行比较，验证了所采用方法的质量。对玻璃结构中所有物种的键合分析突出了由于模拟级联导致的非晶网络连通性的特定结构变化。
