论文标题
在模式耦合理论的临界温度以下的超冷液体中的脆性屈服
Brittle yielding in supercooled liquids below the critical temperature of mode coupling theory
论文作者
论文摘要
提出了剪切下多分散软球模型的分子动力学（MD）计算机模拟。这些仿真的起点是高于模式耦合理论的临界温度，$ t_c $的深冷样品。这些样品借助交换蒙特卡洛技术完全平衡。对于低于$ t_c $的状态，我们确定了寿命$τ_{\ rm lt} $，该$τ_ {\ rm lt} $衡量可以将系统视为无定形固体的时间尺度。 $τ_ {\ rm lt} $的温度依赖性可以由Arrhenius定律很好地描述。 $ t_c $以下的瞬态无定形固态的存在与脆性屈服的可能性有关，这表现为应力 - 应变关系和剪切带的急剧应力下降。我们表明，脆性屈服一方面需要低剪切速率，另一方面，与反剪切率相对应的时间尺度必须较小或$τ_{\ rm lt} $的顺序。这两个条件只能在较大的寿命时间内满足$τ_{\ rm lt} $，即〜对于远低于$ t_c $的状态。
Molecular Dynamics (MD) computer simulations of a polydisperse soft-sphere model under shear are presented. Starting point for these simulations are deeply supercooled samples far below the critical temperature, $T_c$, of mode coupling theory. These samples are fully equilibrated with the aid of the swap Monte Carlo technique. For states below $T_c$, we identify a life time $τ_{\rm lt}$ that measures the time scale on which the system can be considered as an amorphous solid. The temperature dependence of $τ_{\rm lt}$ can be well described by an Arrhenius law. The existence of transient amorphous solid states below $T_c$ is associated with the possibility of brittle yielding, as manifested by a sharp stress drop in the stress-strain relation and shear banding. We show that brittle yielding requires on the one hand low shear rates and on the other hand, the time scale corresponding to the inverse shear rate has to be smaller or of the order of $τ_{\rm lt}$. Both conditions can be only met for large life time $τ_{\rm lt}$, i.e.~for states far below $T_c$.
