We calculated the glassy response of solid He-4 to torsional oscillations assuming a phenomenological glass model. Making only a few assumptions about the distribution of glassy relaxation times in a small subsystem of otherwise rigid solid He-4, we can account for the magnitude of the observed period shift and concomitant dissipation peak in several torsion oscillator experiments. The implications of the glass model for solid He-4 are threefold: (1) The dynamics of solid He-4 is governed by glassy relaxation processes. (2) The distribution of relaxation times varies significantly between different torsion oscillator experiments. (3) The mechanical response of a torsion oscillator does not require a supersolid component to account for the observed anomaly at low temperatures, though we cannot rule out its existence.
Motivated by the concept of partial ergodicity, we present an alternative description of covalent and ionic glassy solids as statistical ensembles of crystalline local minima on the potential energy surface. We show analytically that the radial distribution function (RDF) and powder X-ray diffraction (XRD) intensity of ergodic systems can be rigorously formulated as statistical ensemble averages, which we evaluate for amorphous silicon and glassy silica through the first-principles random structure sampling. We show that using structures with unit cells as small as 24 atoms, we are able to acc…
Sulfide-based glasses and glass-ceramics showing high ionic conductivities and excellent mechanical properties are considered as promising solid-state electrolytes. Nowadays, the computational material techniques with the advantage of low research cost are being widely utilized for understanding, effectively screening and discovering of battery materials. In consideration of the rising importance and contributions of computational studying on the glassy SSE materials, here, this work summarizes the common computational methods utilized for studying the amorphous inorganic materials, review the…
By the adoption of a quaternion orientational order parameter to describe solidification, the topological origins of the thermal transport properties of crystalline and non-crystalline solid states are considered herein. Global orientational order, achieved by spontaneous symmetry breaking, is prevented at finite temperatures for systems that exist in restricted dimensions (Mermin-Wagner theorem). Just as complex ordered systems exist in restricted dimensions in 2D and 1D, owing to the dimensionality of the order parameter, quaternion ordered systems in 4D and 3D exist in restricted dimensions…
用{ \it ab initio}分子动力学方法模拟了三种不同氧化程度下氧化锑的非晶相.的原子和电子结构的非晶相进行了分析，并比较其结晶对应。三氧化物（{ \it α 1，}-Sb $_2$ O $_3$）的无定形结构类似于结晶形式的$β$ -相（Valentinite），与以前的观察结果一致.然而，在松弛的非热结构中，更多的方钠闪石样结构特征是明显的。在{ \it ab initio}热力学框架内计算了非晶相相对于氧化学势的相图。在升高的氧化水平下，与三氧化物相比，所得的四氧化物和五氧化物材料显示出电子结构的明显变化，电子态密度表明随着氧化水平的增加，电子能隙变窄。
Lithium phosphorus oxynitride (LiPON) is an amorphous solid-state lithium ion conductor displaying exemplary cyclability against lithium metal anodes. There is no definitive explanation for this stability due to the limited understanding of the structure of LiPON. We provide a structural model of RF-sputtered LiPON via experimental and computational spectroscopic methods. Information about the short-range structure results from 1D and 2D solid-state nuclear magnetic resonance experiments investigating chemical shift anisotropy and dipolar interactions. These results are compared with first pri…
Glasses and disordered materials are known to display anomalous features in the density of states, in the specific heat and in thermal transport. Nevertheless, in recent years, the question whether these properties are really anomalous (and peculiar of disordered systems) or rather more universal than previously thought, has emerged. New experimental and theoretical observations have questioned the origin of the boson peak and the linear in T specific heat exclusively from disorder and TLS. The same properties have been indeed observed in ordered or minimally disordered compounds and in incomm…
Exploring conformational energy landscape of glassy disaccharides by CPMAS 13C NMR and DFT/GIAO simulations. II. Enhanced molecular flexibility in amorphous trehalose
本文讨论了比较使用化学位移表面来模拟非晶态固体态二糖的实验13 C CPMAS数据，特别注意海藻糖的-1-1键，吡喃糖环之间的-1，4键（乳糖）和暗示呋喃糖环的键（蔗糖）。分子力学与DFT/GIAO从头算方法的结合提供了玻璃中构象分布的可靠结构信息。结果解释为与其他糖相比，海藻糖在非晶态固体状态下具有增强的灵活性。试图将这种性质与玻璃中分子内和分子间氢键网络之间的平衡联系起来。
Synthetic hectorite clay Laponite RD/XLG is composed of disk-shaped nanoparticles that acquire dissimilar charges when suspended in an aqueous media. Owing to their property to spontaneously self-assemble, Laponite is used as a rheology modifier in a variety of commercial water-based products. Particularly, aqueous dispersion of Laponite undergoes liquid - to - solid transition at about 1 volume % concentration. The evolution of the physical properties as dispersion transforms to solid state is reminiscent of physical aging in molecular as well as colloidal glasses. The corresponding soft glas…
As a nontrivial solid state of matter, the glassy-crystal state embraces physical features of both crystalline and amorphous solids, where a long-range ordered periodic structure formed by the mass centers of constituent molecules accommodates orientational glasses. Here, we discover and validate a glassy-crystal state in 2-amino-2-methyl-1,3-propanediol (AMP, C4H11NO2) by neutron scattering and complementary broadband dielectric spectroscopy (BDS) measurements. The freezing process of the dynamic orientational disorder is manifested at relaxation times well described by the Vogel-Fulcher-Tamm…
Continuum modeling of Soft Glassy Materials under shear
Università di Roma “Tor Vergata”（罗马托尔维尔加塔大学）；ENSL, CNRS, Laboratoire de physique（里昂高等师范学校，法国国家科学研究中心，物理实验室）；Univ. de Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière（里昂大学，克莱贝尔·伯纳德里昂第一大学，法国国家科学研究中心，光物质研究所）；Institut Universitaire de France (IUF)（法兰西学院）；Eindhoven University of Technology（埃因霍温理工大学）；CNR-IAC（意大利国家研究委员会应用化学研究所）
Glassy solids may undergo a fluidization (yielding) transition upon deformation whereby the material starts to flow plastically. It has been a matter of debate whether this process is controlled by a specific time scale, from among different competing relaxation/kinetic processes. Here, two constitutive models of cage relaxation are examined within the microscopic model of nonaffine elasto-plasticity. One (widely used) constitutive model implies that the overall relaxation rate is dominated by the fastest between the structural ($α$) relaxation rate and the shear-induced relaxation rate. A dif…
A remark on the negative activation volume for defects in solids
从高于其玻璃化转变温度$T_g$的温度淬火的玻璃态材料的老化过程的演变，当绘制松弛焓与体积减少的关系图时，导致与接近$T_g$的等温压缩率相当的斜率。这一经验结果在早期的出版物中得到了解释（V. Katsika-Tsigourakou，G. E. Zardas J. Non-Cryst. Solids 356（2010）179-180）中描述。在这里，我们表明，相同的模型能够解释固体中的负缺陷激活的罕见情况。
Using molecular simulations and theory, we develop an explicit mapping of the contribution of molecular relaxation modes in glassy thermosets to the shear modulus, where the relaxations were tuned by altering the polarity of side groups. Specifically, motions at the domain, segmental, monomer, and atomic levels are taken from molecular dynamics snapshots and directly linked with the viscoelasticity through a framework based in the lattice dynamics of amorphous solids. This unique approach provides direct insight into the roles of chemical groups in the stress response, including the timescale …
The time evolution of the pore size distributions and mechanical properties of amorphous solids at constant pressure is studied using molecular dynamics simulations. The porous glasses were initially prepared at constant volume conditions via a rapid thermal quench from the liquid state to the glassy region and allowing for simultaneous phase separation and material solidification. We found that at constant pressure and low temperature, the porous network becomes more compact and the glassy systems relocate to progressively lower levels of the potential energy. Although the elastic modulus and…
Yield stress fluids (YSFs) display a dual nature highlighted by the existence of a yield stress such that YSFs are solid below the yield stress, whereas they flow like liquids above it. Under an applied shear rate $\dotγ$, the solid-to-liquid transition is associated with a complex spatiotemporal scenario. Still, the general phenomenology reported in the literature boils down to a simple sequence that can be divided into a short-time response characterized by the so-called "stress overshoot", followed by stress relaxation towards a steady state. Such relaxation can be either long-lasting, whic…
