The thermodynamic properties of Al-Ce melts

Thermodynamic modeling of Al-Ce melts was performed at a total pressure p = 10⁵ Pa in an argon atmosphere over the temperature and concentration ranges 1773–2373 K and 0 ≤ x _Ce ≤ 1, respectively, corresponding to the liquid-phase region of the phase diagram of the system. The concentration and temperature dependences of the thermodynamic characteristics of the melts and the contents of melt components and gas phase components over the melts were calculated, the temperatures, enthalpies, and entropies of the liquid-gas transition were determined, and the phase diagram of the liquid-liquid + gas-gas transition was obtained.     

A first-principles description of liquid BeF2 and its mixtures with LiF: 1. Potential development and pure BeF2

The construction of an interaction potential for BeF2 and its mixtures with LiF on a purely first-principles basis is described. The quality of the representation of the forces on the ions obtained from ab initio electronic structure calculations by various potentials, which include many-body interaction effects to different extents, are considered. The predictions of the properties of pure BeF2 obtained in simulations with a polarizable potential are then compared with experimental values. In the subsequent paper, a more extensive comparison of the predicted properties of LiF-BeF2 mixtures with experiment is considered.     

Vaporization and thermodynamic properties of indium-lead melts

Vapor composition and thermodynamic properties of melts of the In-Pb system were studied by high-temperature mass spectrometry. In the temperature range 780–1170 K, the In_1?x Pb _x melts feature an appreciable positive deviation from the ideal behavior.     

The thermodynamic properties of Al-Si system melts

The thermochemical properties of Al-Si system melts were determined by an improved isoperibolic calorimetry method. The data obtained correlated with the reliable partial and integral enthalpies of mixing reported in the literature. The method developed was used to model the thermodynamic properties of melts with the use of the liquidus coordinates of the phase diagram of the Al-Si system. The modeled and experimental results were in close agreement with each other.     

Excess entropy scaling of transport properties in network-forming ionic melts (SiO(2) and BeF(2))

The regime of validity of Rosenfeld excess entropy scaling of diffusivity and viscosity is examined for two tetrahedral, network-forming ionic melts (BeF(2) and SiO(2)) using molecular dynamics simulations. With decrease in temperature, onset of local caging behavior in the diffusional dynamics is shown to be accompanied by a significant increase in the effect of three-body and higher-order particle correlations on the excess entropy, diffusivity, ionic conductivity, and entropy-transport relationships. The signature of caging effects on the Rosenfeld entropy scaling of transport properties is a distinctly steeper dependence of the logarithm of the diffusivity on the excess entropy in ionic melts. This is shown to be true also for a binary Lennard-Jones glassformer, based on available results in the literature. Our results suggest that the onset of a landscape-influenced regime in the dynamics is correlated with this characteristic departure from Rosenfeld scaling. The breakdown of the Nernst-Einstein relation in the ionic melts can also be correlated with the emerging cooperative dynamics.     

Entropy, diffusivity, and structural order in liquids with waterlike anomalies

The excess entropy, defined as the difference between the entropies of the liquid and the ideal gas under identical density and temperature conditions, is studied as a function of density and temperature for liquid silica and a two-scale ramp potential, both of which are known to possess waterlike liquid state anomalies. The excess entropy for both systems is evaluated using a fairly accurate pair correlation approximation. The connection between the excess entropy and the density and diffusional anomalies is demonstrated. Using the pair correlation approximation to the excess entropy, it can be shown that if the energetically favorable local geometries in the low and high density limits have different symmetries, then a structurally anomalous regime can be defined in terms of orientational and translational order parameters, as in the case of silica and the two-scale ramp system but not for the one-scale ramp liquid. Within the category of liquids with waterlike anomalies, we show that the relationship between the macroscopic entropy and internal energy is sufficient to distinguish between those with local anisotropy and consequent open packings at low densities and those with isotropic interactions but multiple length scales. Since it is straightforward to evaluate the pair correlation entropy and internal energy from simulations or experimental data, such plots should provide a convenient means to diagnose the existence as well as type of anomalous behavior in a range of liquids, including ionic and intermetallic melts and complex fluids with ultrasoft repulsions.     

Vapor formation and thermodynamic properties of the gallium-lead system melts

A vapor composition and thermodynamic properties of melts of the gallium-lead system were studied by high-temperature mass-spectrometry. It was shown on the basis of thermodynamic calculations that Ga_1?x Pb _x melts are characterized by an appreciable positive deviation from the ideal behavior in the temperature range 780–1170 K.     

Simulation of thermodynamic properties of borosilicate melts containing alkaline-earth metal oxides

The possibility for simulation of thermodynamic parameters of MO-B₂O₃-SiO₂ melts (M = Ca, Sr, Ba) in terms of the UNIQUAC associated solution theory was demonstrated using the experimental data obtained previously by high-temperature mass spectrometry (1650–1800 K). The calculated numbers of different bonds formed in the examined melts were found to correlate with the deviations of their thermodynamic parameters from ideality.     

A first-principles description of liquid BeF2 and its mixtures with LiF: 2. Network formation in LiF-BeF2

A polarizable ionic interaction potential, constructed from first-principles calculations, is used to examine the structure, vibrational spectra, and transport properties of molten mixtures of LiF and BeF2 across a range of compositions. The simulations reproduce the experimentally measured vibrational frequencies of the fluoroberyllate (BeF4(2-)) ions, which form in the melt, as well as conductivity and viscosity values across the composition range. Examination of the structures of the melts reveals the emergence of a slowly relaxing network of BeF4 units as the concentration of BeF2 is increased. The relationship between the appearance of the network and the composition dependence of the transport properties is explored.     

液相色谱过量热力学函数变化规律性探讨

本文从溶液热力学和色谱理论推导出过量热力学函数与色谱参数间的关系, 测定了苯的同系物在液-液分配过程中, 过量焓变等函数与流动相组成、样品碳数的线性关系,并求得经验方程式. 同时研究了不同样品焓变和熵变的线性补偿规律. 并试图从溶液理论进行计算.     

Calculating the thermodynamic and structural properties of liquid noble gases

The structural and energy parameters in the liquid branch of the saturation line of noble gases, including ⁴He, are determined.     

Corresponding states theory and thermodynamic properties of liquid alkali metals

According to phenomenological scaling and the law of corresponding states, reduced coordinates F ^*-T ^*, where F* represents the reduced thermodynamic properties (enthalpy of vaporization, speed of sound, surface tension, saturated liquid density) and T ^* is the reduced temperature, are introduced for the prediction of the thermodynamic properties of alkali metals. Values of the thermodynamic properties from the melting point up to boiling point are correlated. It has been shown that the correlation between reduced thermodynamic properties, as well as with the reduced temperature, can be expressed as a unique straight-line plot with a linear correlation coefficient of 0.9998. The proposed correlation has a simple form for easy calculation, requires only the melting and boiling point parameters, which are usually easy to acquire, and can predict the thermodynamic properties from the melting temperature up to the boiling temperature accurately.     

Ionic liquid crystals: synthesis and mesomorphic properties of dimeric 2,4,6-triarylpyrylium tetrafluoroborates

The synthesis of some dimeric pyrylium salts is described. The link between the two cationic parts of the molecule can be flexible or rigid. Surprisingly, the starting dimeric chalcones with a rigid link exhibit monotropic columnar hexagonal phases. Results concerning the spectroscopic and mesomorphic properties of the pyrylium salts and the chalcones are given.     

Ionic liquid crystals: synthesis and mesomorphic properties of dimeric 2,4,6-triarylpyrylium tetrafluoroborates

The synthesis of some dimeric pyrylium salts is described. The link between the two cationic parts of the molecule can be flexible or rigid. Surprisingly, the starting dimeric chalcones with a rigid link exhibit monotropic columnar hexagonal phases. Results concerning the spectroscopic and mesomorphic properties of the pyrylium salts and the chalcones are given.     

Structural and thermodynamic properties of different phases of supercooled liquid water

Computer simulation results are reported for a realistic polarizable potential model of water in the supercooled region. Three states, corresponding to the low density amorphous ice, high density amorphous ice, and very high density amorphous ice phases are chosen for the analyses. These states are located close to the liquid-liquid coexistence lines already shown to exist for the considered model. Thermodynamic and structural quantities are calculated, in order to characterize the properties of the three phases. The results point out the increasing relevance of the interstitial neighbors, which clearly appear in going from the low to the very high density amorphous phases. The interstitial neighbors are found to be, at the same time, also distant neighbors along the hydrogen bonded network of the molecules. The role of these interstitial neighbors has been discussed in connection with the interpretation of recent neutron scattering measurements. The structural properties of the systems are characterized by looking at the angular distribution of neighboring molecules, volume and face area distribution of the Voronoi polyhedra, and order parameters. The cumulative analysis of all the corresponding results confirms the assumption that a close similarity between the structural arrangement of molecules in the three explored amorphous phases and that of the ice polymorphs I(h), III, and VI exists.     

Synthesis and properties of two new liquid crystals: an analytical and thermodynamic study

Synthesis, analytical performances, thermodynamic and surface properties of two new liquid crystals substituted with poly(ethylene oxide) chains are described. The first of them is N,N'-diphenyl-[4-[2,3,4-tri[2-(2-metoxyethoxy)ethoxy]benzylidene]i mine]piperidine (LC1) and the second is 2-hydroxy-3-methyl-4-[4-[2-(2-butoxyethoxy)ethoxy]] 4'-[4-[2-(2-butoxyethoxy)ethoxy]styryl]azobenzene (LC2). The nematic ranges of the two liquid crystals, determined by differential scanning calorimetry do not interfere. The analytical and thermodynamic studies of LC1 and LC2 in the solid, nematic and liquid state were done using a series of appropriate solutes. Comparison of the analytical performances shows a better efficiency in the nematic state.