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We present a structural analysis of glasses formed by mix of SiO2 and B2O3 glass formers with soda and lime modifiers (Na2O and CaO), which provide a good testing ground for Stochastic Agglomeration Theory. With local structural units properly identified, we can reproduce the one-parameter glass transition temperature T_g (z) curve for the family of (0.75-z) SiO_2 + 0.15 Na_2O + 0.10 CaO + z B_2O_3 glasses studied experimentally by Smedskjaer et al.

The manner in which metallic glasses fail under external loading is known to correlate well with those glasses' Poisson's ratio $ν$: low-$ν$ (compressible) glasses typically feature brittle failure patterns with scarce plastic deformation, while high-$ν$ (incompressible) glasses typically fail in a ductile manner, accompanied by a high degree of plastic deformation and extensive liquid-like flow. Since the technological utility of metallic glasses depends on their ductility, materials scientists have been concerned with fabricating high-$ν$ glassy alloys. To shed light on the underlying micromechanical origin of high-$ν$ metallic glasses, we employ computer simulations of a simple glass-forming model with a single tunable parameter that controls the interparticle-potential's stiffness. We show that the presented model gives rise to ultra high-$ν$ glasses, reaching $ν\!=\!0.45$ and thus exceeding the most incompressible laboratory metallic glass. We discuss the possible role of the so-called unjamming transition in controlling the elasticity of ultra high-$ν$ glasses. To this aim, we show that our higher-$ν$ computer glasses host relatively softer quasilocalized glassy excitations,

The glassy dynamics of dense active matter have recently become a topic of interest due to their importance in biological processes such as wound healing and tissue development. However, while the liquid-state properties of dense active matter have been studied in relation to the glass transition of active matter, the solid-state properties of active glasses have yet to be understood. In this work, we study the structural fluctuations in the active glasses composed of self-propelled particles. We develop a formalism to describe the solid-state properties of active glasses in the harmonic approximation limit and use it to analyze the displacement fields in the active glasses. Our findings reveal that the dynamics of high-frequency normal modes become quasi-static with respect to the active forces, and consequently, excitations of these modes are significantly suppressed. This leads to a violation of the equipartition law, suppression of particle displacements, and the apparent collective motion of active glasses. Overall, our results provide a fundamental understanding of the solid-state properties of active glasses.

We measured the shear viscosity of 14 metallic glasses differing with their mixing entropy $ΔS_{mix}$. It is found that the viscosity at the glass transition temperature $T_g$ significantly increases with $ΔS_{mix}$. Using calorimetric data, we calculated the excess entropy of all glasses $ΔS$ with respect to their maternal crystalline states as a function of temperature. It is shown that the excess entropy $ΔS$ both at room temperature and at $T_g$ \textit{decreases} with $ΔS_{mix}$. It is concluded that glasses with "high mixing entropy" $ΔS_{mix}$ correspond to MGs with \textit{low} excess entropy $ΔS$. The origin of the increased shear viscosity at $T_g$ of glasses with high $ΔS_{mix}$ is determined by their reduced excess entropy $ΔS$.

Vapor deposition can yield glasses that are more stable than those obtained by the traditional melt-quenching route. However, it remains unclear whether vapor-deposited glasses are "allowable" or "forbidden," that is, if they are equivalent to glasses formed by cooling extremely slowly a liquid or if they differ in nature from melt-quenched glasses. Here, based on reactive molecular dynamics simulation (MD) of silica glasses, we demonstrate that the allowable or forbidden nature of vapor-deposited glasses depends on the temperature of the substrate and, in turn, is found to be encoded in their medium-range order structure.

We carried out molecular dynamics simulations (MD) using realistic empirical potentials for the vapor deposition (VD) of CuZrAl glasses. VD glasses have higher densities and lower potential and inherent structure energies than the melt-quenched glasses for the same alloys. The optimal substrate temperature for the deposition process is 0.625$\times T_\mathrm{g}$. In VD metallic glasses (MGs), the total number of icosahedral like clusters is higher than in the melt-quenched MGs. Surprisingly, the VD glasses have a lower degree of chemical mixing than the melt-quenched glasses. The reason for it is that the melt-quenched MGs can be viewed as frozen liquids, which means that their chemical order is the same as in the liquid state. In contrast, during the formation of the VD MGs, the absence of the liquid state results in the creation of a different chemical order with more Zr-Zr homonuclear bonds compared with the melt-quenched MGs. In order to obtain MGs from melt-quench technique with similarly low energies as in the VD process, the cooling rate during quenching would have to be many orders of magnitude lower than currently accessible to MD simulations. The method proposed in this m

Glasses show vibrational properties that are markedly different to those of crystals which are known as phonons. For example, excess low-frequency modes (the so-called boson peak), vibrational localization, and strong scattering of phonons have been the most discussed topics, and a theoretical understanding of these phenomena is challenging. To address this problem, computational simulations are a powerful tool, which have been employed by many previous works. In this chapter, we describe simulation methods for studying the vibrational properties of glasses (and any solid-state materials). We first present a method for studying vibrational eigenmodes. Since vibrational motions of particles are excited along eigenmodes, the eigenmodes are fundamental to descriptions of vibrational properties. The eigenmodes in glasses are non-phonon modes in general, and some of them are even localized in space. We next present a method of analysing phonon transport, which is also crucial for understanding vibrational properties. Since phonons are not eigenmodes in glasses, they are decomposed into several different, non-phonon eigenmodes. As a result, phonons in glasses are strongly scattered. In a

We find that the density dependence of the glass transition temperature of Lennard-Jones (LJ) and Weeks-Chandler-Andersen (WCA) systems can be predicted from properties of the zero-temperature ($T=0$) glasses. Below a crossover density $ρ_s$, LJ and WCA glasses show different structures, leading to different vibrational properties and consequently making LJ glasses more stable with higher glass transition temperatures than WCA ones. Above $ρ_s$, structural and vibrational quantities of the $T=0$ glasses show scaling collapse. From scaling relations and dimensional analysis, we predict a density scaling of the glass transition temperature, in excellent agreement with simulation results. We also propose an empirical expression of the glass transition temperature using structural and vibrational properties of the $T=0$ glasses, which works well over a wide range of densities.

Within the wide class of disordered materials, spin glasses occupy a special place because of their conceptually simple definition of randomly interacting spins. Their modelling has triggered spectacular developments of out-of-equilibrium statistical physics, as well analytically as numerically, opening the way to a new vision of glasses in general. "Real" spin glasses are disordered magnetic materials which can be very diverse from the chemist's point of view, but all share a number of common properties, laying down the definition of generic spin glass behaviour. This paper aims at giving to non-specialist readers an idea of what spin glasses are from an experimentalist's point of view, describing as simply as possible their main features as they can be observed in the laboratory, referring to numerous detailed publications for more substantial discussions and for all theoretical developments, which are hardly sketched here. We strived to provide the readers who are interested in other glassy materials with some clues about the potential of spin glasses for improving their understanding of disordered matter. At least, arousing their curiosity for this fascinating subject will be c

Bioactive glasses (BGs) and glass-ceramics (BGCs) have become a diverse family of materials being applied for treatment of many medical conditions. The traditional understanding of bioactive glasses and glass-ceramics pins them to bone-bonding capability without considering the other fields where they excel, such as soft tissue repair. We attempt to provide an updated definition of BGs and BGCs by comparing their structure, processing, and properties to those of other biomaterials. The proposed modern definition allows for consideration of all applications where the BGs and BGCs are currently used in the clinic and where the future of these promising biomaterials will grow. The new proposed definition of a bioactive glass is "a non-equilibrium, non-crystalline material that has been designed to induce specific biological activity". The proposed definition of a bioactive glass-ceramic is "an inorganic, non-metallic material that contains at least one crystalline phase within a glassy matrix and has been designed to induce specific biological activity." BGs and BGCs can bond to bone and soft tissues or contribute to their regeneration. They can deliver a specified concentration of in

Unlike crystals, glasses age or devitrify over time, reflecting their non-equilibrium nature. This lack of stability is a serious issue in many industrial applications. Here, we show by numerical simulations that the devitrification of quasi-hard-sphere glasses is prevented by suppressing volume fraction inhomogeneities. A monodisperse glass known to devitrify with `avalanche'-like intermittent dynamics is subjected to small iterative adjustments to particle sizes to make the local volume fractions spatially uniform. We find that this entirely prevents structural relaxation and devitrification over aging time scales, even in the presence of crystallites. There is a dramatic homogenization in the number of load-bearing nearest neighbors each particle has, indicating that ultra-stable glasses may be formed via `mechanical homogenization'. Our finding provides a physical principle for glass stabilization and opens a novel route to the formation of mechanically stabilized glasses.

A range of ferroic glasses, magnetic, polar, relaxor and strain glasses, are considered together from the perspective of spin glasses. Simple mathematical modelling is shown to provide a possible conceptual unification to back similarities of experimental observations, without considering all possible complexities and alternatives.

We report a strain rate (equivalent to experimental observation time) induced glass transition in model SrCaYbMg(Li)Zn(Cu) metallic glasses at room temperature. A critical strain rate, equivalent to glass transition temperature, is found for the strain rate induced a glassy state to liquid-like viscoplastic state translation. The results show that the observation time, equivalent to temperature and stress, is a key parameter for the glass transition. A three-dimension glass transition phase diagram involved in time, temperature and stress in metallic glasses is established for understanding the nature of the metallic glasses.

We give a simple demonstration of the formula relating the glass transition temperature, $T_g$, to the molar concentration $x$ of a modifier in two types of glasses: binary glasses, whose composition can be denoted by $X_nY_m+xM_pY_q$, with ^$X$ an element of III-rd or IV-th group (e.g. B, or Si, Ge), while $M_pY_q$ is an alkali oxide or chalcogenide; next, the network glasses of the type $A_xB_{1-x}$, e.g. $Ge_xSe_{1-x}$, $Si_xTe_{1-x}$, etc. After comparison, this formula gives an exact expression of the parameter $β$ of the modified Gibbs-Di Marzio equation.

Previously observed non-Arrhenius behavior in fast ion conducting glasses [\textit{Phys.\ Rev.\ Lett.}\ \textbf{76}, 70 (1996)] occurs at temperatures near the glass transition temperature, $T_{g}$, and is attributed to changes in the ion mobility due to ion trapping mechanisms that diminish the conductivity and result in a decreasing conductivity with increasing temperature. It is intuitive that disorder in glass will also result in a distribution of the activation energies (DAE) for ion conduction, which should increase the conductivity with increasing temperature, yet this has not been identified in the literature. In this paper, a series of high precision ionic conductivity measurements are reported for $0.5{Na}_{2}{S}+0.5[x{GeS}_{2}+(1-x){PS}_{5/2}]$ glasses with compositions ranging from $0 \leq x \leq 1$. The impact of the cation site disorder on the activation energy is identified and explained using a DAE model. The absence of the non-Arrhenius behavior in other glasses is explained and it is predicted which glasses are expected to accentuate the DAE effect on the ionic conductivity.

In this talk I will show that usual spin glasses are a peculiar kind of Abelian gauge theory. I will shortly review the techniques used to study them. At the end I will consider more general models (e.g. spin glasses based on non Abelian gauge group) and I will discuss the relevance of these models to real glasses. Finally I will derive from first principles a generalised Vogel-Fulcher law for the divergence of the characteristic time near the glass transition.

We review the approach to glasses based on the replica formalism. The replica approach presented here is a first principle's approach which aims at deriving the main glass properties from the microscopic Hamiltonian. In contrast to the old use of replicas in the theory of disordered systems, this replica approach applies also to systems without quenched disorder (in this sense, replicas have nothing to do with computing the average of a logarithm of the partition function). It has the advantage of describing in an unified setting both the behaviour near the dynamic transition (mode coupling transition) and the behaviour near the equilibrium `transition' (Kauzmann transition) that is present in fragile glasses. The replica method may be used to solve simple mean field models, providing explicit examples of systems that may be studied analytically in great details and behave similarly to the experiments. Finally, using the replica formalism and some well adapted approximation schemes, it is possible to do explicit analytic computations of the properties of realistic models of glasses. The results of these first-principle computations are in reasonable agreement with numerical simulat

Transparent glasses of BaNaB9O15 (BNBO) were fabricated via the conventional melt-quenching technique. The amorphous and the glassy nature of the as-quenched samples were respectively, confirmed by X-ray powder diffraction (XRD) and differential scanning calorimetry (DSC). The glass transition and crystallization parameters were evaluated under non-isothermal conditions using DSC. The correlation between the heating rate dependent glass transition and the crystallization temperatures was discussed and deduced the Kauzmann temperature for BNBO glass-plates and powdered samples. The values of the Kauzmann temperature for the plates and powdered samples were 776 K and 768 K, respectively. Approximation-free method was used to evaluate the crystallization kinetic parameters for the BNBO glass samples. The effect of the sample thickness on the crystallization kinetics of BNBO glasses was also investigated.