Searcharxiv⌕ Search

arXiv subjects

Vladimir Belostotsky

Publications and source records attributed to Vladimir Belostotsky.

6 recordsLinked to original sources
arXiv2022

Thermodynamic approach to liquid-to-glass transformation as an arrest transition in polydisperse solution

Thermodynamic multi-component solution solidification approach to liquid-to-glass transition is proposed and actual mechanisms underlying vitrification, other than viscous slowdown, are identified. Due to polydisperse aggregation in liquid state, glass-forming liquids, irrespective of chemical composition, appear to be mixtures of various quasi-components whose thermodynamic quantities shall be expressed not in terms of molar concentrations of actual chemical components, but in terms of relative concentrations of dominant structural units. Thermodynamically, any glass-former is expected to behave as multi-component solution and solidify in continuous temperature range between apparent liquidus and solidus temperatures that can be identified as glass-transition range. Using extended irreversible thermodynamics of polydisperse solutions it is demonstrated that upon quenching, diffusional and Brownian mass transport in such solutions is negated within heat removal timescale, which results in dynamical arrest of nucleation and growth in clusters and solid-liquid phase separation. Rapid solution solidification proceeds via successive cluster freezing in continuous temperature range, in line with cluster size dispersity, which can be described in terms of percolation in static polydisperse fractal ensemble where glass transition temperature naturally emerges as percolation threshold. Multi-component solution solidification framework is shown to be reconcilable qualitatively and quantitatively with the Mode Coupling - Random First Order Transition scenario. Finally, it is demonstrated that liquid-to-glass transformation is thermodynamic liquid-to-solid phase transition, glassy state of matter appears to be solid supersaturated solution of defects in otherwise perfect matrix, and the true equilibrium structure which glass is unable access is a crystalline one.

cond-mat.mtrl-sci↗
arXiv2021

Multicomponent solution solidification with arrested phase separation model for liquid-to-glass transition

Due to nonuniform aggregation in liquid state, from the thermodynamic point of view any glass-forming liquid in the vicinity of the liquid-to-solid phase transition temperature, irrespective of its actual chemical composition, shall be described in terms of a complex multicomponent solution whose comprised of the same chemical elements components have characteristic atomic arrangement deviating to various extent from the thermodynamic ground state with respect to the size, shape, density, structure, and stoichiometry. Therefore, glass transition appears to be a process of non-equilibrium solidification of multicomponent solution upon its rapid cooling. The essential feature of this process is that the attempts of the liquid and solid phases of the solidifying solution to separate out are largely arrested due to quenching. Thus, the solidification occurs in the absence of solid-liquid interface, so the substance in the liquid-to-glass transition region is observed behaving like fluid with rapidly growing viscosity that reflects the formation of mechanically rigid and stable bound configurations. It is shown that glass transition shall be classified as phase transition in multicomponent solutions and not a standalone phenomenon.

cond-mat.dis-nn↗
arXiv2010

Peculiarities of the defect model for the mixed mobile ion effect in mixed cation glasses

Peculiarities of mixed cation effect in ternary glasses whose composition involves alkali and non-alkali unicharged ions and/or alkaline earth ions are explored within context of defect model for mixed mobile ion effect (V. Belostotsky, J. Non-Cryst. Solids (2007)). In mixed alkaline earth glasses mixed cation effect is observed as in ionic diffusivity as well as in the glass transition temperature reflecting the fact that movement of dissimilar ions of unequal size is accompanied by formation of intrinsic defects in glass matrix when mobile ions enter foreign sites. It is qualitatively similar to that in mixed alkali glasses although quantitatively it is much less pronounced due to lower mobility of alkaline earth ions. In mixed cation glasses whose composition involves dissimilar mobile ions with ionic radii close to each other 'classical' mixed mobile ion effect is not observed in sense we face it in mixed alkali glasses. In alkali alkaline earth glasses like xNa2O-(1-x)CaO-SiO2 and xK2O-(1-x)BaO-SiO2 energy landscape is comprised of regular unicharged alkali sites and double-charged alkaline-earth sites, and mobile ions of both types can utilize either vacant sites without their rearrangement. This leads to increase in apparent diffusivity of alkaline-earth species when their concentration decreases which is opposite to what is reported for mixed alkali glasses. Mixed cation effect in the transition temperature of such glasses is not observed which is clear indication that site rearrangement involving generation of intrinsic defects does not occur when a mobile ion enters a foreign site. Similar picture is observed in Na-Ag phosphate glasses where mixed cation effect in ionic conductivity is anomalously low because dissimilar ions have almost equal ionic radii and can utilize either vacant sites without their rearrangement and intrinsic defect formations in nearest glass matrix

cond-mat.mtrl-sci↗
arXiv2009

Defect model for the mixed mobile ion effect revisited: an importance of deformation rates

The progress in understanding the behavior of glassy mixed ionic conductors within the concept of the defect model for the mixed mobile ion effect (V. Belostotsky, J. Non-Cryst. Solids 353 (2007) 1078) is reported. It is shown that in a mixed ionic conductor (e.g., mixed alkali glass) containing two or more types of dissimilar mobile ions of unequal size sufficient local strain arising from the size mismatch of a mobile ion entering a foreign site can not be, in principle, absorbed by the surrounding network-forming matrix without its damage. Primary site rearrangement occurs immediately, on the time scale close to that of the ion migration process, through the formation of intrinsic defects in the nearest glass network. Neither anelastic relaxation below glass transition temperature, Tg, nor viscoelastic or viscous behavior at or above Tg can be expected being observed in this case because the character of the stress relaxation in a wide temperature range is dictated above all by the deformation rates employed locally to the adjacent network-forming matrix. Since the ion migration occurs on the picosecond time scale, the primary rearrangement of the glass network adjacent to an ionic site occurs at rates orders of magnitude higher than those of the critical minimum values, so the matrix demonstrates brittle-elastic response to the arising strain even at temperatures well above Tg, which explains, among other things, why mixed alkali effect is observable in glass melts.

cond-mat.mtrl-sci↗
arXiv2006

Defect model for the mixed mobile ion effect

This paper presents a new defect model for the mixed mobile ion effect. The essential physical concept involved is that simultaneous migration of two unlike mobile ions in mixed ionic glass is accompanied by expansion or contraction of the guest-occupied sites with distortion of surrounding glass matrix; in many cases, an intensity of the local stresses in glass matrix surrounding ionic sites occupied by foreign ions is much greater than, or at least comparable to the glass network binding energy. Hence, when the stress exceeds the breaking threshold, relaxation occurs almost immediately via the rupture of the bonds in the nearest glass matrix with generation of pairs of intrinsic structural defects. The specificity of the mechanism of defect generation leads to the clustering of negatively charged defects, so that rearranged sites act as high energy anion traps in glass matrix. This results in the immobilization of almost all minority mobile species and part of majority mobile species, so mixed mobile ion glass behaves as single mobile ion glass of much lower concentration of charge carriers. Generation of defects leads also to the depolymerization of glass network, which in turn results in the reduction of the glass viscosity and Tg as well as in the compaction of glass structure (thermometer effect). The magnitude of the mixed mobile ion effect is defined by the size mismatch of unlike mobile ions, their total and relative concentrations, the binding energy of the glass-forming network, and temperature. Although the proposed model is based upon the exploration of alkali silicate glass-forming system, the approach developed here can be easily adopted to other mixed ionic systems such as crystalline and even liquid ionic conductors.

cond-mat.mtrl-sci↗