揭示方肩系统的复杂玻璃态动力学：模拟和理论
Unveiling the complex glassy dynamics of square shoulder systems: simulations and theory
摘要：
我们进行了广泛的分子动力学（MD）模拟，补充模式耦合理论（MCT）的计算，方肩（SS）模型，一个纯粹的排斥性的潜力，其中的硬核是由有限的肩膀补充。对于该模型的单组分版本，MCT预测[Sperl { \it et al.}物理修订信函{ \bf 104}，145701（2010）]在冷却和压缩时扩散异常的存在以及玻璃-玻璃转变的发生。在模拟中，我们专注于一个非结晶的二元混合物，其中，在调查的肩宽，显示冷却后的扩散，但不是等温压缩的非单调行为。此外，我们发现存在一个断开的玻璃玻璃线的相图，在两个高阶奇点结束。这些点产生的对数依赖性的密度衰减因子以及subdiffusive行为的均方位移，虽然与附近的液体玻璃化转变的干扰。我们还进行了新的MCT计算作为输入的部分结构因子内MD，确认模拟结果。两个硬球玻璃的存在下，不同的只是在他们的硬核长度，揭示，表明两者之间的简单竞争是足够的创造一个相当复杂的动力学行为。
英文摘要：
We performed extensive molecular dynamics (MD) simulations, supplemented by Mode Coupling Theory (MCT) calculations, for the Square Shoulder (SS) model, a purely repulsive potential where the hard-core is complemented by a finite shoulder. For the one-component version of this model, MCT predicted [Sperl {\it et al.} Phys. Rev. Lett. {\bf 104}, 145701 (2010)] the presence of diffusion anomalies both upon cooling and upon compression and the occurrence of glass-glass transitions. In the simulations, we focus on a non-crystallising binary mixture, which, at the investigated shoulder width, shows a non-monotonic behaviour of the diffusion upon cooling but not upon isothermal compression. In addition, we find the presence of a disconnected glass-glass line in the phase diagram, ending in two higher-order singularities. These points generate a logarithmic dependence of the density correlators as well as a subdiffusive behaviour of the mean squared displacement, although with the interference of the nearby liquid-glass transition. We also perform novel MCT calculations using as input the partial structure factors obtained within MD, confirming the simulation results. The presence of two hard sphere glasses, differing only in their hard core length, is revealed, showing that the simple competition between the two is sufficient for creating a rather complex dynamical behaviour.
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