Heterophase liquid states: Thermodynamics, structure, dynamics

An overview of theoretical results and experimental data on the thermodynamics, structure and dynamics of the heterophase glass-forming liquids is presented. The theoretical approach is based on the mesoscopic heterophase fluctuations model (HPFM) developed within the framework of the bounded partition function approach. The Fischer cluster phenomenon, glass transition, liquid-liquid transformations, parametric phase diagram, cooperative dynamics and fragility of the glass-forming liquids is considered.Comment: 24 pages, 9 figure

Thermodynamics of gas–liquid colloidal equilibrium states: hetero-phase fluctuations

Following on from two previous JETC (Joint European Thermodynamics Conference) presentations, we present a preliminary report of further advances towards the thermodynamic description of critical behavior and a supercritical gas-liquid coexistence with a supercritical fluid mesophase defined by percolation loci. The experimental data along supercritical constant temperature isotherms (T >= T-c) are consistent with the existence of a two-state mesophase, with constant change in pressure with density, rigidity, (dp/d rho) (T), and linear thermodynamic state-functions of density. The supercritical mesophase is bounded by 3rd-order phase transitions at percolation thresholds. Here we present the evidence that these percolation transitions of both gaseous and liquid states along any isotherm are preceded by pre-percolation hetero-phase fluctuations that can explain the thermodynamic properties in the mesophase and its vicinity. Hetero-phase fluctuations give rise to one-component colloidal-dispersion states; a single Gibbs phase retaining 2 degrees of freedom in which both gas and liquid states with different densities percolate the phase volume. In order to describe the thermodynamic properties of two-state critical and supercritical coexistence, we introduce the concept of a hypothetical homo-phase of both gas and liquid, defined as extrapolated equilibrium states in the pre-percolation vicinity, with the hetero-phase fractions subtracted. We observe that there can be no difference in chemical potential between homo-phase liquid and gaseous states along the critical isotherm in mid-critical isochoric experiments when the meniscus disappears at T = T-c. For T > T-c, thermodynamic states comprise equal mole fractions of the homo-phase gas and liquid, both percolating the total phase volume, at the same temperature, pressure, and with a uniform chemical potential, stabilised by a positive finite interfacial surface tension.info:eu-repo/semantics/publishedVersio

On chemical bonding of Helium with hcp-Beryllium

Chemical inertness is the key property of helium determining its solubility, distribution and accumulation kinetics in metals. Against all expectations, our ab initio calculations show a substantial chemical bonding between He and Be atoms in the hcp-Be matrix when He occupies a non-symmetric position in a basal plane.Comment: Revised version of manuscript, 4 pages, 4 figure

On correlated heterogeneities of glass-forming liquids

The thermodynamics and structure of glass-forming liquids are considered within the framework of the heterophase fluctuation (HPF) model. The main goal of the theory developed is to fined for a description of the long-range correlations (LRC) of the density fluctuations known as the Fischer cluster. The van der Waals approximation of the HPF model shows that the liquid can have an isolated solid-fluid critical point analogous to the critical point of a gas-liquid system. Heterophase fluctuations in the form of solidlike noncrystalline and fluidlike clusters can have LRC in a narrow vicinity of the critical point. An analysis shows that the properties of the conventional critical fluctuations differ from those of the Fisher cluster. This forces one to look for another explanation of the observed LRC in glass-forming liquids. Large configurational entropy of liquids and glasses is a manifestation of multiplicity of the short-range ordering of molecules in the amorphous solidlike and fluidlike clusters. The multiplicity of short-range order results in structural heterogeneities. Random-field Ginzburg-Landau equations for the HPFs are deduced taking into account the structural heterogeneities. The random field is generated by these heterogeneities. It is found that at least three characteristic correlation scales are inherent to the HPF: the radius of local order, r₀, which is comparable with the radius of the first coordination sphere; the random-field-controlled radius of critical fluctuations, Rc; the average correlation length of fractal aggregations formed by the correlated domains (the domains have size ~ Rc), xav. The length xav is the characteristic size of the Fischer cluster. The conditions for the appearance of the listed correlations are deduced by requiring that they provide minimization of the free energy of the system. The annealing kinetics and dynamics (the ultraslow modes) of the Fischer cluster are described

Correlation phenomena in the glass-forming liquids

A theory of the long-range correlations of density fluctuations is presented for the glass-forming liquids. The supercooled heterophase liquid (HPL) is considered as composed of solid-like and fluid-like species with many types of the short-range order (SRO). The random field Ginzburg-Landau (GL) equations are deduced for the HPL. The variety of the SRO originates the local random fields. It is shown that optimization of the free energy gives rise to the medium and long-range correlations of the random fields and order parameter. Conditions for observation of such correlations are deduced. Time dependent GL equations are used to establish the ultra-slow dynamics and annealing kinetics of the long-range correlations