Phase States of Europium Selenites in Aqueous Medium and in Thermal Analysis

The solubility isotherm of the system Eu₂O₃-SeO₂-H₂O was studied at 100°C. Certain amounts of the obtained selenites (normal and acid) were subjected to thermal analysis. The intermediate phases were isolated and chemical and X-ray phase analysis was made. The scheme of thermal decomposition was determined. This revised version was published online in August 2006 with corrections to the Cover Date.     

Monte Carlo Simulation of the Topology and Conformational Behavior of Hyperbranched Molecules: Pd–Diimine‐Catalyzed Polyethylene

A kinetic Monte Carlo model was developed to simulate the polymerization of ethylene with palladium–α‐diimine catalyst wherein hyperbranched molecules are formed through a chain‐walking mechanism. The total degree of branching and the distribution of short branches obtained with the model agree well with reported ¹³C NMR experimental results. Different chain topologies were generated by varying the probability of chain walking, P_w , which controls the competition between chain‐walking and monomer insertion. Molecular Monte Carlo simulations were subsequently conducted to study the conformations of isolated molecules (created by the kinetic Monte Carlo scheme) to relate molecular shape and topology. Our results provide evidence that the topology varies from predominantly linear with many short branches at low P_w to a densely branched, globular structure at high P_w . In contrast to experimental observations, our results for the molecular weight (N) dependence of the radius of gyration (R_g ∝ N^v) indicate that the branching topology has an effect on this relation, i. e., high‐P_w molecules have a smaller scaling exponent v. The simulated N‐dependence of the second virial coefficient exhibits a similar behavior. We also discuss the unusual conformational behavior of highly branched polymers obtained when P_w → 1.     

Research of the Central Core in Bi12SiO20 Crystals

The structure of the so-called “central core” within Czochralski grown Bi₁₂SiO₂₀ crystals is investigated by the laser projection. A finer structure with a number of optical inhomogeneities with irregular forms and sizes about 2–3 μm is observed within the core. The conditions for facet growth and absorption of impurities on the facets are described. Positron lifetime measurements are carried out within and outside the core. The results show a higher concentration of defects in regions within the core. The optical rotatory power in regions within and outside of the core was measured, too. An evaluation of the distribution of the different structural units and the dopants is made. Some suppositions about the kind and the role of the defective center are given.     

Analysis of the diameteral response of a czochralski crystal II. The melt temperature — furnace temperature relation

The paper is the second in a series which presentes results on the small-signal diametral response of a Czochralski crystal grown in a resistively heated furnace to variations in heater temperature and pull rate. Here it is shown that the small-signal bulk melt temperature variation is related to the small-signal furnace temperature variation via a first order linear differential equation.     

Tribochemical synthesis of halogen-phosphate luminophores

The possibility of tribochemical synthesis of Ca₁₀(PO₄)₆ · (F, Cl)₂SbMn is shown. It was proved that the synthesis with the initial compounds CaHPO₄ · 2H₂O or β-Ca₃(PO₄)₂ is realized 1–2 hours faster than the synthesis when CaHPO₄ is used.     

Thermal analysis of the selenites of the ternary system Nd2O3-SeO2-H2O AT 100°C

The solubility isotherm of the system Nd₂O₃-SeO₂-H₂O at 100°C was studied and drawn. All possible selenites of neodymium were obtained and characterized. Thermal decomposition of all phases in the system was studied and its mechanism was described. This revised version was published online in August 2006 with corrections to the Cover Date.     

Bridging continuum and statistical thermodynamics via equations of state and the density of states

The connection between molecular force fields and equations of state (EoS) is typically established at the level of predicted quantities, e.g., by comparing simulation data and EoS data. In this paper we show how an EoS can be used to extract the density of states (Omega) of a system thus establishing a deeper connection between EoSs and statistical thermodynamics. We also show how such an EoS Omega can be used to aid molecular simulation methods designed to map out Omega (like the multicanonical approach). Central to the implementation of these ideas is the fact that the configurational Omega is related to thermodynamic properties accessible by an EoS via Boltzmann's equation. Sample calculations are presented for the Omega relevant to isothermal-isobaric and grand canonical ensemble simulations using the hard-sphere system and the Lennard-Jones system as model fluids, and the Carnahan-Starling EoS and a cubic EoS, respectively, as thermodynamic models.     

A study of the compounds present in the three-component system Dy2O3-SeO2-H2O at 100°C

The solubility isotherm of the system Dy₂O₃-SeO₂-H₂O at 100°C was studied and drawn. The selenites present in the system were identified and isolated. A thorough TG, DTG and DTA analysis was made. By modelling the conditions of TG, DTG and DTA analysis, the phases of the thermal decomposition were isolated and identified. The chemistry of the reaction was described.     

Physicochemical study on gadolinium selenites

The solubility isotherm of the system Gd₂O₃-SeO₂-H₂O at 100°C was studied. The compounds of the three-component system were identified by the Schreinemakers' method as well as by chemical and X-ray phase analyses. Simultaneous TG and DTA analyses of all compounds of the system were made. The mechanism of thermal decomposition was described.     

Electrotransport properties of ions in aqueous solutions of H<Subscript>2</Subscript>SeO<Subscript>4</Subscript> and Na<Subscript>2</Subscript>SeO<Subscript>4</Subscript>

Coefficients of self-diffusion, absolute speeds of movement of ions and the activation energy of electrical conductivity are found from the conductance measurements of aqueous solutions of selenic acid and sodium selenate at different concentrations in a temperature range of 288–318 K. Both the Stokes and effective radii of ions and their hydrate numbers at 298 K are calculated. The obtained results are interpreted in the frames of Samoilov theory on positive and negative hydration of ions.