W Vanderlugt

Resistivity calculations for liquid Na-Cs and K-Cs alloy systems

Abstract The resistivities of liquid Na-Cs alloys are calculated as a function of the composition. A version of the Heine-Abarenkov model potential is used with special attention to three corrections: first, concentration-dependent core shifts are introduced, secondly, effective masses are taken into account and thirdly, many-electron effects are included by taking the Toigo and Woodruff dielectric function. For the partial structure factors of the alloys the solutions of the Percus-Yevick equations for a binary mixture of hard spheres are applied. The discrepancy between theoretical and experimental values is of the order of twenty percent.

Electrical resistivities and phase separation of liquid lithium-sodium alloys

Abstract The resistivities of liquid lithium-sodium alloys have been determined as a function of temperature for alloy compositions covering the entire concentration range. When the resistivity is plotted as a function of concentration, the nonlinear terms corresponding to the Nordheim rule appear to be remarkably small. A shallow minimum was found at the lithium-rich end of the composition range. As the measurements were carried out from 500°C down to temperatures below the phase separation temperature, the temperature coefficient of the resistivity could be calculated. Additionally, the immiscibility loop of the phase diagram has been determined. Calculations along the lines of the diffraction model provide satisfactory agreement with experiment but appear to be rather sensitive to one of the input parameters.

TEMPERATURE-DEPENDENT INTERCHANGE ENERGY OF THE LIQUID ALLOY NA0.85CS0.15

Abstract Small-angle x-ray diffraction data on the liquid alloy Na0.85Cs0.15 at temperatures from 80 to 190°C are presented. The analysis will be given on the basis of the Flory model, introducing a temperature dependent interchange energy. This concept brings more consistency in the results of diffraction, calorimetric and EMF measurements.

Concentration fluctuations in molten Li0.62Na0.38

Inelastic neutron scattering spectra of molten 7Li0.62Na0.38 have been measured using the IN6 time of flight spectrometer at the Institut Laue-Langevin. The composition is close to the critical composition and has been chosen such that coherent scattering is only from Scc(Q, ω). Measurements have been made at temperatures between 725 and 571 K and the critical temperature for phase separation determined to be 576 ± 2 K. The inverse correlation length for concentration fluctuations κ < 0.1 A-1 and consequently only very slight evidence of critical narrowing of the quasi-elastic peak is observed in the range 0.3 < Q < 2 A-1 covered. No changes in the inelastic scattering spectrum are observed other than a change in intensity consistent with the change in temperature. The results are therefore in accord with those expected for a well-behaved system at the critical point for phase separation with long-range concentration fluctuations. The critical indices are found to be η < 0.04, ν ≅ 0.5 and γ ≅ 1.

ELECTRICAL TRANSPORT PROPERTIES AND PHASE-DIAGRAM OF LIQUID BINARY LITHIUM-MAGNESIUM SYSTEM

Abstract The electrical resistivities of a number of liquid lithium-magnesium alloys, covering the entire composition range, have been measured as a function of temperature from 675°C down to the liquidus. Additionally, for the same alloy compositions, the temperature of the liquidus has been determined. Calculations of the resistivity were carried out within the framework of the diffraction model, using Heine-Abarenkov-Shaw type model potentials with screening according to Toigo and Woodruff. For the partial structure factors, solutions for hard-sphere potentials of the Percus-Yevick equation for binary systems, with suitably chosen hard sphere parameters, were used. On the same basis, calculations of the thermopower were carried out. As for sodium-caesium alloys, the non-local character of the model potential leads to puzzling results.

The electrical resistivity of liquid potassium-rubidium, rubidium-caesium and sodium-potassium alloys

Abstract The electrical resistivities ϱ and their temperature dependences dϱ/d T of liquid K-Rb and Rb-Cs alloys have been determined experimentally. Additionally, the resistivities of Na-K alloys were re-investigated in order to check earlier experiments. The results are interpreted theoretically on the basis of the diffraction model.

LI-7 KNIGHT-SHIFT IN LIQUID LI-MG ALLOYS

Abstract The 7 Li Knight shift in liquid Li-Mg alloys is found to be a linear, decreasing function of the magnesium concentration. This result is explained qualitatively in terms of transfer of Fermi electrons from the Li to the Mg cells, in agreement with calculations of the local density of states in solid LiMg by Inglesfield. The Korringa enhancement increases monotonically when magnesium is added to lithium.

RADIAL-DISTRIBUTION FUNCTIONS OF LIQUID NA AND CS

Abstract Radial distribution functions of liquid sodium and caesium at 100°C have been calculated by the method of molecular dynamics with interionic pair potentials derived from Heine-Abarenkov-Shaw type model potential. The results were found to be in good agreement with recent experimental data.

Calculations of entropies and specific heats of liquid metallic elements in the Percus-Yevick phonon approximation

Abstract Some further calculations of entropies, S , and specific heats, C p , have been carried out within the framework of the Percus-Yevick phonon theory. In particular, the following points were investigated: (1) the influence on S and C p of the experimental structure factors used in the calculations and (2) the applicability to liquid metallic elements with a non-simple liquid structure.

Dynamics of molten Au-Cs Alloys

Abstract We have measured inelastic neutron scattering spectra of the molten alloys Au 0.5 Cs 0.5 and Au 0.4 Cs 0.6 using the time-of-flight spectrometer IN5 at the Institut Laue-Langevin. Only small differences are observed between the spectra of the two samples, despite the fact that the former has a typically ionic conductivity, and the latter a typically metallic conductivity, two orders of magnitude higher. These results are consistent with a model where the Au 0.4 Cs 0.6 melt consists of segregated ionic (Au - Cs + ) regions and metallic (Cs + e - ) regions.