Properties of the glass transition as a mixture of jamming and random organization

颗粒系统中密度增加或温度降低时动力学的急剧减慢已经被探索了很长时间。然而，这种玻璃态动力学，特别是玻璃化转变的许多性质仍然不清楚。在拟议的项目中，我们希望采用一个模型系统，以调查的玻璃化转变，其微观起源，以及它的关系，非热干扰过渡。无热干扰通常通过使用使软球系统内的重叠最小化而不跨越能量势垒的协议来获得，而在有限温度下的玻璃态动力学的情况下，有可能跨越能量势垒。最近的研究表明，在低温极限下的玻璃化转变与无热堵塞转变有很大的不同。在拟议的项目中，我们将研究一个模型系统，其中粒子首先随机分布，然后在每一步中重叠的粒子被确定性或随机地取代。在随机方向上的位移的情况下，观察到所谓的随机组织转变，而对于纯确定性位移，协议对应于用于获得非热干扰的协议。我们研究的模型系统的混合协议，包括确定性和随机位移，后者对应于在一个软球系统中的能量障碍的交叉。用这种混合方案观察到的转变对应于软球系统的玻璃化转变。在初步模拟中，我们确实发现，在随机位移的概率很小但不为零的情况下，过渡与纯粹确定性的干扰过渡有很大不同。因此，该模型系统适合于研究在小但非零温度下的玻璃化转变与非热干扰转变之间的差异。在拟议的项目中，我们希望开发一个定量映射的结果从模型系统到玻璃动力学的软球系统。此外，我们将确定玻璃化转变的临界行为，并探索玻璃化转变的微观原因，这可能与接触渗滤转变有关。总之，通过研究一个模型包装系统，我们希望获得更好的知识和更深入的了解玻璃化转变的性质，以及它的起源上的粒子分辨的基础上。

The dramatic slowdown of the dynamics in particulate systems for increasing density or decreasing temperature has been explored for a long time. However, many properties of such glassy dynamics and especially of the glass transition are still not understood. In the proposed project, we want to employ a model system in order to investigate the glass transition, its microscopic origin, as well as its relation to the athermal jamming transition. Athermal jamming usually is obtained by using a protocol that minimizes the overlaps within a soft sphere system without crossing energy barriers while in case of with glassy dynamics at finite temperatures it is possible to cross energy barriers. Recent studied indicate that the glass transition in the limit of small temperatures significantly differs from the athermal jamming transition. Within the proposed project, we will study a model system where particles are first randomly distributed and then in each step overlapping particles are displaced either deterministically or randomly. In case of displacements in random directions the so-called random organization transition is observed, while for purely deterministic displacements the protocol corresponds to the protocol used to obtain athermal jamming. We study the model system for a mixed protocol consisting both of deterministic and random displacements where the latter correspond to the crossing of energy barriers in a soft sphere system. The transition observed with such a mixed protocol corresponds to the glass transition of a soft sphere system. In preliminary simulations we have indeed found that in case of a small but non-zero probability for random displacements the transition differs significantly from the purely deterministic jamming transition. Therefore, this model system is suitable to study the difference between the glass transition at small but non-zero temperatures and the athermal jamming transition. In the proposed project, we want to develop a quantitative mapping of results obtained from the model system onto the glassy dynamics of a soft sphere system. Furthermore, we will determine the critical behavior of the glass transition and explore the microscopic reasons for the glass transition, which might be related to a contact percolation transition. In summary, by studying a model packing system, we expect to gain better knowledge and a deeper understanding of the properties of the glass transition as well as of its origin on a particle-resolved basis.