It has recently become possible to prepare ultrastable glassy materials characterised by structural relaxation times which vastly exceed the duration of any feasible experiment. Similarly, new algorithms have led to the production of ultrastable computer glasses. Is it possible to obtain a reliable estimate of a structural relaxation time that is too long to be measured? We review, organise, and critically discuss various methods to estimate very long relaxation times. We also perform computer simulations of three dimensional ultrastable hard spheres glasses to test and quantitatively compare some of these methods for a single model system. The various estimation methods disagree significantly and it is not yet clear how to accurately estimate extremely long relaxation times.
Theoretical model for the structural relaxation time in co-amorphous drugs
我们提出了一个简单的方法来研究非晶药物的结构弛豫时间和玻璃化转变。非晶材料被建模为一组大小相等的硬球。本文用与Kramer理论相联系的Elementary集体非线性Langevin方程理论计算了硬球流体几十年的结构弛豫时间。然后,一个新的热映射从一个真正的材料到一个有效的硬球流体提供了温度依赖的弛豫时间,这可以与实验相比。数值结果定量同意与以前的实验具有不同的重量比的药物二元混合物。我们进行实验,以测试我们的计算依折麦布-辛伐他汀-Kollidon VA 64混合物。我们的方法将提供一个简单而全面的描述非晶复合材料的玻璃态动力学。
We theoretically investigate structural relaxation and activated diffusion of glass-forming liquids at different pressures using both the Elastically Collective Nonlinear Langevin Equation (ECNLE) theory and molecular dynamics (MD) simulation. An external pressure restricts local motions of a single molecule within its cage and triggers the slowing down of cooperative mobility. While the ECNLE theory and simulation generally predict a monotonic increase of the glass transition temperature and dynamic fragility with pressure, the simulation indicates a decrease of fragility as pressure above 10…
Liquid water is well-known for its intriguing thermodynamic anomalies in the supercooled state. The phenomenological two-state models - based on the assumption of the existence of two types of competing local states (or, structures) in liquid water - have been extremely successful in describing water's thermodynamic anomalies. However, the precise structural features of these competing local states in liquid water still remain elusive. Here, we have employed a geometrical order parameter-free approach to unambiguously identify the two types of competing local states -- entropically and energet…
Effects of Cooling Rate on Structural Relaxation in Amorphous Drugs: Elastically Collective Nonlinear Langevin Equation Theory and Machine Learning Study
We study supercooled dynamics in quantum hard-sphere liquid using quantum mode-coupling formulation. In the moderate quantum regime, classical cage effects lead to slower dynamics compared to strongly quantum regime, where tunneling overcomes classical caging, leading to faster relaxation. As a result, the glass transition critical density can become significantly higher than for the classical liquids. Perturbative approach is used to solve time dependent quantum mode-coupling equations to study in detail the dynamics of the supercooled liquid in moderate quantum regime. Similar to the classic…
Relaxation of quenched structural glasses: descent in a stiffening caging potential over inflection-point 'speed bumps'
Institute of Theoretical Physics, Chinese Academy of Sciences(中国科学院理论物理研究所);School of Physical Sciences, University of Chinese Academy of Sciences(中国科学院大学物理科学学院);Wenzhou Institute, University of Chinese Academy of Sciences(中国科学院大学温州研究院)
Role of tip size, orientation, and structural relaxations in first-principles studies of magnetic exchange force microscopy and spin-polarized scanning tunneling microscopy