标题： 过冷Cu-Zr-Al玻璃形成液体中的成核不稳定性 显示英文标题

标题： Nucleation instability in super-cooled Cu-Zr-Al glass-forming liquids

摘要： 在过冷液体和玻璃的计算机模拟中，一些代表实际玻璃形成系统的特定类别的通用模型扮演着特殊角色。最近，人们发现最广泛使用的模型玻璃形成体之一——Kob-Andersen二元Lennard-Jones混合物——在相当长的分子动力学模拟中会结晶，并且实际上在大系统尺寸下是一个非常差的玻璃形成体。因此，由于迄今为止只考虑了相对较小的系统尺寸和较短的时间尺度，我们对模型玻璃形成体结晶稳定性的理解还远不完整。在这里，我们针对两种近年来在数值研究Cu-Zr-(Al)块状金属玻璃中被广泛使用的嵌入原子模型来解决这个问题。我们将${\rm Cu_{64.5}Zr_{35.5}}$和${\rm Cu_{46}Zr_{46}Al_{8}}$合金视为具有高玻璃形成能力的合金。通过研究它们在连续冷却和等温退火过程中的结构演化，我们观察到两个系统在足够长的模拟中都会形核，尽管${\rm Cu_{46}Zr_{46}Al_{8}}$的临界形核时间要高出一个数量级。此外，${\rm Cu_{64.5}Zr_{35.5}}$在大系统尺寸（$N > 20,000$）下实际上对结晶是不稳定的。两个系统都通过形成不同类型的四面体密堆Laves相而结晶。我们发现，两个系统在液态和玻璃态下的结构中都含有相当数量的多面体簇。我们认为，模拟的${\rm Cu_{64.5}Zr_{35.5}}$合金的形核不稳定性是由于其成分非常接近具有C15 Laves相结构的稳定${\rm Cu_2 Zr}$化合物的成分。 显示英文摘要

摘要： Special role in computer simulations of supercooled liquid and glasses is played by few general models representing certain classes of real glass-forming systems. Recently, it was shown that one of the most widely used model glassformers -- Kob-Andersen binary Lennard-Jones mixture -- crystalizes in quite lengthy molecular dynamics simulations and, moreover, it is in fact a very poor glassformer at large system sizes. Thus, our understanding of crystallization stability of model glassformers is far from complete due to the fact that relatively small system sizes and short timescales have been considered so far. Here we address this issue for two embedded atom models intensively used last years in numerical studies of Cu-Zr-(Al) bulk metallic glasses. We consider ${\rm Cu_{64.5}Zr_{35.5}}$ and ${\rm Cu_{46}Zr_{46}Al_{8}}$ alloys as those having high glass-forming ability. Exploring their structural evolution at continuous cooling and isothermal annealing, we observe that both systems nucleate in sufficiently lengthy simulations, though ${\rm Cu_{46}Zr_{46}Al_{8}}$ demonstrate order of magnitude higher critical nucleation time. Moreover, ${\rm Cu_{64.5}Zr_{35.5}}$ is actually unstable to crystallization for large system sizes ($N > 20,000$). Both systems crystallize with the formation of tetrahedrally close packed Laves phases of different types. We reveal that structure of both systems in liquid and glassy state contains comparable amount of polytetrahedral clusters. We argue that nucleation instability of simulated ${\rm Cu_{64.5}Zr_{35.5}}$ alloy is due to the fact that its composition is very close to that for stable ${\rm Cu_2 Zr}$ compound with C15 Laves phase structure.