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

干扰和随机组织混合的玻璃化转变特性

• 批准号: 262587878
• 负责人: Professor Dr. Michael Schmiedeberg
• 金额: --
• 依托单位: Lehrstuhl für Theoretische Physik I
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/262587878?language=en
• 关键词: Properties; glass; transition; mixture; jamming

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.

长期以来，人们一直在探索粒子系统中由于密度增加或温度降低而导致的动力学急剧放缓。然而，这种玻璃化动力学的许多性质，特别是玻璃化转变的性质仍然不清楚。在这个项目中，我们想用一个模型系统来研究玻璃化转变，它的微观起源，以及它与非热干扰转变的关系。非热干扰通常通过在不跨越能量垒的情况下使用最小化软球系统内重叠的协议来获得，而在有限温度下的玻璃动力学情况下，可以跨越能量垒。最近的研究表明，在小温度极限下的玻璃化转变与非热干扰转变有很大的不同。在提议的项目中，我们将研究一个模型系统，其中粒子首先随机分布，然后在每个步骤中重叠的粒子确定性或随机地位移。对于随机方向的位移，观察到所谓的随机组织过渡，而对于纯确定性位移，该协议对应于用于获得无热干扰的协议。我们研究了一个由确定性和随机位移组成的混合协议的模型系统，其中随机位移对应于软球系统中能量垒的交叉。用这种混合协议观察到的转变对应于软球系统的玻璃化转变。在初步的模拟中，我们确实发现，在随机位移的概率很小但非零的情况下，这种过渡与纯粹确定性干扰的过渡有很大的不同。因此，该模型系统适用于研究小但非零温度下的玻璃化转变与非热干扰转变的区别。在提议的项目中，我们希望将从模型系统获得的结果定量映射到软球体系统的玻璃动力学上。此外，我们将确定玻璃化转变的临界行为，并探讨玻璃化转变的微观原因，这可能与接触渗透转变有关。总之，通过研究一个模型包装系统，我们期望在粒子分解的基础上对玻璃化转变的性质以及它的起源有更好的认识和更深入的理解。