The existence of nanoscale ductility during the fracture of silicate glasses remains controversial. Here, based on molecular dynamics simulations coupled with topological constraint theory, we show that nano-ductility arises from the spatial heterogeneity of the atomic network's rigidity. Specifically, we report that localized floppy modes of deformation in under-constrained regions of the glass enable plastic deformations of the network, resulting in permanent change in bond configurations. Ultimately, these heterogeneous plastic events percolate, thereby resulting in a non-brittle mode of fracture. This suggests that nano-ductility is intrinsic to multi-component silicate glasses having nanoscale heterogeneities.
Structure and properties of magnesium silicate and borate melts and glasses were investigated by using newly parameterized interaction potentials in molecular dynamics simulations and compared with those of calcium silicate and borate. The competition between the depolymerization of the silica network and the formation of new bonds with modifier ions leads to the enhancement of the elastic moduli with increasing modifier content in alkaline earth silicate glasses. Compared with calcium silicate, the higher elastic moduli of magnesium silicate result from a higher connectivity of the overall gl…
Linking Thermal History to Shear Band Interaction and Macroscopic Ductility in Metallic Glasses
Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences（中国科学院宁波材料技术与工程研究所）；Institute of Advanced Magnetic Materials, College of Materials & Environmental Engineering, Hangzhou Dianzi University（杭州电子科技大学材料与环境工程学院先进磁性材料研究所）；State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences（中国科学院力学研究所非线性力学国家重点实验室）；School of Engineering Science, University of Chinese Academy of Sciences（中国科学院大学工程科学学院）；Beijing Computational Science Research Center（北京计算科学研究中心）
We use \textit{ab initio} molecular dynamics simulations to investigate the properties of the dry surface of pure silica and sodium silicate glasses. The surface layers are defined based on the atomic distributions along the direction ($z-$direction) perpendicular to the surfaces. We show that these surfaces have a higher concentration of dangling bonds as well as two-membered (2M) rings than the bulk samples. Increasing concentration of Na$_2$O reduces the proportion of structural defects. From the vibrational density of states, one concludes that 2M rings have a unique vibrational signature …
The effect of tensile stress applied during cooling of binary glasses on the potential energy states and mechanical properties is investigated using molecular dynamics simulations. We study the three-dimensional binary mixture that was first annealed near the glass transition temperature and then rapidly cooled under tension into the glass phase. It is found that at larger values of the applied stress, the liquid glass former freezes under higher strain and its potential energy is enhanced. For a fixed cooling rate, the maximum tensile stress that can be applied during cooling is reduced upon …
For small tension the response of a solid to an applied stress is given by Hooke's law. Outside this linear regime the relation between stress and strain is no longer universal and at present there is no satisfactory insight on how to connect for disordered materials the stress-strain relation to the microscopic properties of the system. Here we use atomistic computer simulations to establish this connection for the case of silicate glasses containing modifiers. By probing how in the highly non-linear regime the stress-strain curve depends on composition, we are able to identify the microscopi…
We use large-scale simulations to investigate the dynamic fracture of silica and sodium-silicate glasses under uniaxial tension. The stress-strain curves demonstrate that silica glass is brittle whereas the glasses rich in Na show pronounced ductility. A strong composition dependence is also seen in the crack velocity which is on the order of 1800 m/s for glasses with low Na concentration and decreases to 700 m/s if the concentration is high. We find that during the fracture of Na-rich glasses very irregular cavities as large as 3-4 nm form ahead of the crack front, indicating the presence of …
Density is one of the most commonly measured or estimated materials properties, especially for glasses and melts that are of significant interest to many fields, including metallurgy, geology, materials science and sustainable cements. Here, two types of machine learning (ML) models (i.e., random forest (RF) and artificial neural network (ANN)) have been developed to predict the room-temperature density of glasses in the compositional space of CaO-MgO-Al2O3-SiO2-TiO2-FeO-Fe2O3-Na2O-K2O-MnO (CMASTFNKM), based on ~2100 data points mined from ~140 literature studies. The results show that the RF …
The original electronic structure of the Pb$^{2+}$ ion explains its particular structural role in crystalline phases and silicate glasses. After a description of the structural role of lead in crystalline phases (PbO, silicates), this chapter presents a summary of the main structural studies carried out on glasses from the SiO$_2$-PbO, SiO$_2$-PbO-R$_2$O (R: alkaline) and SiO$_2$-PbO-Al$_2$O$_3$ systems, using various spectroscopic and simulation techniques.
In this work, we use molecular dynamics simulations to study the enhancement of surface over bulk diffusion (surface enhanced diffusion) in (PbO)x(SiO2)1-x glasses. This work is motivated to better understand surface diffusion in glasses and its connection to fragility, and to enhance surface diffusion in silica and related glasses for greater thermodynamic stability during vapor-deposition. By adding PbO to silica, the fragility of glass increases continuously for 10% <= x <= 70% during experiments. The increase in fragility may correspond to an increase in surface enhanced diffusion, as frag…
Oxide glasses are made of a network of glass former polyhedra, and modifiers which have a role in neutralizing the charge of the glass former polyhedra or depolymerize the glass network. The effect of the modifier content on the structure and properties of the glass are to some extent, well known. However, the effect of the type of modifiers on the clustering and the tendency to form a phase separation in the glass is not investigated in detail and still not fully understood until now. Here, we use molecular dynamics to investigate the effect of the modifier type on the structure and the clust…
Multiscale Experimental Evidence of a Transitory State in the HDA-LDA Transition in Alumino-sodo-silicate Glasses
Institut Lumière Matière UMR CNRS 5306, Université Claude Bernard Lyon 1, CNRS（里昂第一大学物质与光研究所）；Institute of Glass and Ceramics, Department of Materials Science and Engineering, Friedrich Alexander University Erlangen Nuremberg（埃尔朗根-纽伦堡弗里德里希·亚历山大大学玻璃与陶瓷研究所）
Linking Topological Medium Range Order and Density-Wave Coherence to Metallic Glass Ductility
The Ohio State University（俄亥俄州立大学）；University of Michigan（密歇根大学）；Federal Institute of Materials Research and Testing（联邦材料研究与测试研究所）；Seoul National University（首尔国立大学）；Denison University（丹尼森大学）；Korea Basic Science Institute（韩国基础科学研究所）
Using molecular dynamics simulations we investigate the dependence of the structural and vibrational properties of the surfaces of sodo-silicate glasses on the sodium content as well as the nature of the surface. Two types of glass surfaces are considered: A melt-formed surface (MS) in which a liquid with a free surface has been cooled down into the glass phase and a fracture surface (FS) obtained by tensile loading of a glass sample. We find that the MS is more abundant in Na and non-bridging oxygen atoms than the FS and the bulk glass, whereas the FS has higher concentration of structural de…
Boson peak and medium-range elastic heterogeneity in calcium silicate hydrate probed by terahertz spectroscopy and low-temperature calorimetry
College of Architecture and Civil Engineering, Beijing University of Technology（北京工业大学建筑与土木工程学院）；Dalian Institute of Chemical Physics, Chinese Academy of Sciences（中国科学院大连化学物理研究所）；School of Environment and Safety Engineering, North University of China（中北大学环境与安全工程学院）；Department of Civil Engineering, Taiyuan University of Technology（太原理工大学土木工程学院）；State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences（中国科学院力学研究所非线性力学国家重点实验室）；School of Materials Science and Engineering, Southeast University（东南大学材料科学与工程学院）；College of Civil and Transportation Engineering, Shenzhen University（深圳大学土木与交通工程学院）；Faculty of Innovation Engineering, Macau University of Science and Technology（澳门科技大学创新工程学院）
Terahertz-driven four-wave mixing at glass surfaces: Probing vibrational resonances and structural regimes
Université Savoie Mont Blanc, Université Grenoble Alpes, Grenoble INP, and CNRS（萨瓦蒙布朗大学、格勒诺布尔阿尔卑斯大学、格勒诺布尔理工学院和法国国家科学研究中心）；University of Bordeaux and CNRS（波尔多大学和法国国家科学研究中心）
