Nanosystem Research Institute (NRI), National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan.
J Chem Phys. 2012 Jul 14;137(2):024510. doi: 10.1063/1.4730613.
We report a first-principles molecular-dynamics study of the relaxation dynamics in liquid silicon (l-Si) over a wide temperature range (1000-2200 K). We find that the intermediate scattering function for l-Si exhibits a compressed exponential decay above 1200 K including the supercooled regime, which is in stark contrast to that for normal "dense" liquids which typically show stretched exponential decay in the supercooled regime. The coexistence of particles having ballistic-like motion and those having diffusive-like motion is demonstrated, which accounts for the compressed exponential decay in l-Si. An attempt to elucidate the crossover from the ballistic to the diffusive regime in the "time-dependent" diffusion coefficient is made and the temperature-independent universal feature of the crossover is disclosed.
我们报告了一项关于液态硅（l-Si）在很宽的温度范围内（1000-2200 K）弛豫动力学的第一性原理分子动力学研究。我们发现，液态硅的中间散射函数在 1200 K 以上表现出压缩指数衰减，包括过冷区，这与通常在过冷区表现出拉伸指数衰减的正常“密集”液体形成鲜明对比。证明了具有弹道运动的粒子和具有扩散运动的粒子共存，这解释了 l-Si 的压缩指数衰减。尝试阐明“时变”扩散系数中从弹道到扩散的转变，并揭示了转变的温度无关的普遍特征。
