金属玻璃形成液体微秒量级弛豫动力学的计算机模拟研究

The properties of glassy materials are intimately related to their forming liquids. Recent studies have demonstrated there are many interesting relaxation processes that will occur in metallic glass forming liquids at the timescale of microseconds, such as the decoupling of the α and β relaxations, liquid-liquid transitions and fragile-strong transitions. These processes provide a window for the design of new metallic glasses with exceptional properties. However, impended by the crystallization of metallic glass forming liquids, it is very difficult to study them in experiments. Moreover, the current molecular dynamics simulations are usually shorter than this time-scale (usually shorter than 1/10 microseconds). Therefore, these issues are still open controversy. In this proposal, we will investigate these topics by large-scale molecular dynamics simulations. We will take advantages of the newly developed computational techniques, such as massive parallelization and the accelerations by graphic processing units (GPU). Our results are expect to provide important clues for these controversy and shed light on the developments of new metallic glasses.

非晶态材料的性质与其液体密切相关。最近研究表明，在微秒量级的弛豫时间尺度上，金属玻璃形成液体会发生一系列重要的物理过程，如α和β弛豫的解耦合、液体-液体相变、液体脆度的强-弱转变等。它们为新型金属玻璃材料的设计提供了窗口。然而，由于金属过冷液体的结晶化影响，实验上很难对这些现象进行直接观察和定量研究。另外，目前的计算机模拟也尚未达到这样的时间尺度。因此，这些问题一直颇具争议。本研究将采用大规模并行计算、图形处理器加速等先进计算技术，通过分子动力学模拟，研究金属玻璃形成液体在微秒量级时间尺度的弛豫动力学，为解决这些争议提供线索；为新型金属玻璃研制提供理论依据。

金属过冷液体具有丰富的弛豫过程，然而由于快速结晶的影响，目前实验上很难直接观察和定量研究。本研究旨在通过微秒量级弛豫模拟以解决此难题。申请人按照计划执行，通过对金属玻璃形成液体的分子动力学模拟，使得计算时间尺度达到几十微秒--几乎是目前分子模拟的极限时间。在模拟上成功的观察到了，α和β弛豫的解耦合过程，并阐明了其相关机理。发现过冷液体和金属玻璃中存在原子链状协同运动；并证明这种运动是β弛豫的微观起源。预测了过冷液体和金属玻璃中存在一种新的α2弛豫过程，并通过实验得到证实。微秒量级弛豫模拟为理解金属玻璃形成液体的本质提供了新的认识，为新型金属玻璃研制提供了有用理论见解。