Cesare Sinistri

Binary Systems Formed by Lead Bromide with (Li, Na, K, Rb, Cs and Tl)Br: a DTA and Diffractometric Study

The phase diagrams of the systems PbBr2 + MeBr (Me = L i , Na, K, Rb, Cs, Tl) have been measured by visual and DTA methods. The structures and the thermal characteristics of the intermediate compounds have been pointed out by X-ray diffractometric technique and by DTA-calorimetric measurements, respectively. Moreover, the thermodynamic behaviour of these systems has been discussed

Binary Systems Formed by Alkali Bromides with Barium or Strontium Bromide

By DTA and visual methods the phase diagrams of the ten binary systems formed by lithium, sodium, potassium, rubidium and cesium bromide with barium or strontium bromide have been drawn. Moreover, the fusion thermal effects regarding the eutectics and the congruent compounds singled out in the systems have been evaluated. The general thermodynamic behaviour of these systems is discussed in comparison with the ideal one.

Thermodynamic Properties of Solid Systems AgCl + NaCl and AgBr + NaBr from Miscibility Gap Measurements

Abstract Miscibility gaps for the solid systems AgCl + NaCl and AgBr+NaBr have been measured by a high temperature X-ray technique. For the two studied systems the solubility curves are very nearly symmetrical in respect to the compositions xNaCl = .513 and xNaBr = .506, while the upper critical temperature are 198 °C for AgCl + NaCl and 285 °C for AgBr+NaBr. The thermodynamic properties of the two solid systems have been calculated using only experimental solubility data. Values of activity and of enthalpy of mixing were estimated and compared with those reported in literature.

Miscibility Gaps in Fused Salts. Note X. The Reciprocal Ternary System K, Li/Br, F

Solid-liquid and liquid-liquid equilibria in the reciprocal ternary system K, Li/Br, F were fully measured. The projection of the miscibility gap occupies 20.8% of the composition square; the upper critical point of the gap is along the stable diagonal at 953°C and xLIF = 0.70. Attempts to predict the liquid-liquid equilibria by means of the conformal ionic solution theory using temperature independent interaction parameters lead to an incorrect symmetry of the gap. The symmetry can be improved if the temperature dependence of the interaction parameters of the binary mixtures is taken into account.

Miscibility Gaps in Fused Salts. Note XI. Systems Formed with Silver Halides and Lithium or Sodium Halides

Abstract The salt families formed with silver halides and lithium or sodium halides were studied in order to investigate demixing in the liquid state. In particular, measurements were carried out on the stable diagonals of the 12 pertinent reciprocal ternaries. Liquid-liquid equilibria were found to occur in the 10 mixtures containing LiF, NaF, LiCl, LiBr and NaCl (the last one only in the presence of Agl). The miscibility gap, however, could be fully measured only on the four mixtures AgBr+LiCl, Agl + LiCl, AgI+LiBr and Agl+NaCl: for these and for the mixture AgI+ NaBr an “a priori” prediction of the gap was possible on the basis of current thermodynamic theories.

Miscibility Gaps in Fused Salts. Note XII. Systems Formed with Thallium (I) Halides and Lithium or Sodium Halides: the Ternary Li, Tl/Cl, I

Abstract Demixing was investigated in the molten salt families formed with thallium (I) halides and lithium or sodium halides. Measurements were carried out on the twelve stable diagonals of the corresponding reciprocal ternary mixtures. Liquid-liquid equilibria were found in the three systems TlCl+LiF, TlBr+LiF and TlI+LiCl while in the two systems formed with Til and LiF or NaF measurements could not be carried out owing to the thermal instability of Til. The reciprocal ternary Li, Tl/Cl, I exhibits demixing in a temperature range which is convenient for investigation: therefore the whole composition square was studied. The upper critical solution point of the gap lies along the stable diagonal at 734°C and xLiCl = 0.58. The projection of the stratification lens occupies 38.8% of the composition square. Moreover an “a priori” prediction of the liquid-liquid equilibria was carried out by means of the conformal ionic solutiontheory.

Monte Carlo Calculations on Molten Silver Bromide

Using crystal data in the range 20-300 °C, the AgBr interionic pair potentials were calculated. By means of these potentials the melt was computer simulated with the Monte Carlo method at three different temperatures (694, 1000 and 1778 K). The system thus obtained is relaxed and it behaves as if an important cohesive force, like the homopolar one, would be lacking. It was empirically proved that if the interionic repulsive potentials are reduced by about 40% the experimental values of the density and of the internal energy are reproduced.

Thermodynamic and Structural Properties of Molten CsCl as Obtained by Computer Simulation

CsCl was computer simulated using the Monte Carlo (MC) method on the basis of interionic pair potentials. Calculations were carried out at constant pressure (1 atm) and at different temperatures covering the liquid phase. The thermodynamic and structural properties thus obtained were in good agreement with the corresponding experimental values when available. A discussion of these properties in relation to those of CsBr and Csl was also carried out. Finally the polarization energy of CsCl along with those of CsBr and Csl, was compared with the results that can be obtained using simpler models recently proposed

Monte Carlo Computations on Molten Caesium Bromide

Abstract Molten CsBr was computer simulated tat 1 atm and four different temperatures using the Monte Carlo method. Structural and thermodynamic properties of the melt were obtained on the basis of pair potentials. In particular, radial distribution functions, volume, and energy with its coulomb, dipole-dipole, and repulsive components were determined. Separately, the polarization energy was also evaluated: this quantity increases with increasing temperature and ranges between 2 and 4% of the total energy.

Interionic Potentials for Some Alkali Halides from Crystal Data Measured at Different Temperatures

Values at different temperatures of lattice constants and their derivatives with respect to T. and of elastic constants were used to obtain the derivatives with respect to the minimum interionic distance of the repulsive potentials for the crystals CsCl, CsBr, ClI, NaCl, KCl and KBr. The derivatives thus calculated were then subjected to a computer fitting to yield the aij and b constants of the interionic repulsive pair potential: Rφij = aij exp{ - brij}.