块体金属玻璃结构-动力学关联模拟研究的临界模型尺度

The critical model size for simulating the structuredynamics correlation in bulk metallic glasses

原子尺度模拟是当前理解金属玻璃体系的无序结构及其构效关系的有效方法.基于分子动力学模拟,本文以代表性金属玻璃Cu_(5)0Zr_(50)为研究对象,系统地研究了块体金属玻璃体系的原子结构和动力学行为的有限尺度效应.通过研究发现,其结构短程序对模型尺寸并不敏感,但其动力学性质却表现出明显的尺寸相关性.通过定量计算可知,当立方体模型所含原子数低于~2000时,金属玻璃体系的结构短程序特征和结构弛豫之间的相关性发生退简并,但其结构弛豫时间和动力学非均匀性依然遵循简并的普适关系.本文的结论给出了结构弛豫和动力学非均匀性之间存在本征关联的有力证据,并第一次明确给出了在没有表面效应的情况下基于计算模拟研究块体金属玻璃结构、动力学及其关联所需要的临界模型尺度.

Computational simulation provides an effective way of understanding the disordered structure and structureproperty relationships for metallic glass systems.Here,we systematically investigated the finite-size effects of the static structure and dynamical behaviors in a three-dimensional Cu50Zr50 model metallic glass via classical molecular dynamics(MD)simulations.It was found that the local structure is insensitive to the system size while the dynamical properties present evident finite-size effects.The decoupling between local structure and relaxation dynamics in the investigated supercooling emerges when the system contains less than~2000 atoms.However,the collapse can be observed between the structural relaxation time and the dynamical heterogeneity for different sized systems across the whole range of our investigation.Our results support the intrinsic link between the structural relaxation time and dynamic heterogeneity and reveal the critical simulated system size for representing the structural origins of dynamics in bulk metallic glass with ignorable surface effects.