Interference Functions, Pair Distribution Functions and Electron Transport Properties of Liquid Mercury-Indium Alloys

Abstract

X-ray diffraction patterns of liquid Hg-In alloys with 5, 12, 25, 35, 42, 50 and 62 atomic percent In were measured at room temperature (25°C). The interference and radial distribution functions, I(K) and 4 π r2 ρ(r), respectively, were refined by an error analysis program. The position K1=4π sin Θ1/λ of the first peak maximum of I(K) does not change upon alloying, i. e., K1=2.29 A-1. The interference function of In plotted in reduced coordinates K/K1 agrees with that calculated from the hard sphere model with a packing density of 45%. A small asymmetry of the first peak towards larger K values might be discernible in In, whereas the Hg and Hg-In interference functions show a relatively large asymmetry, and their subsequent peaks appear at larger K/K1 values than those of the hard sphere model and In. The interatomic distances r1 and the numbers of electrons ηE in the first coordination shell show only a small deviation from a linear relationship when plotted as a function of concentration. Since 1(K) for K<2 kF, where kF is the FERMI radius, are rather similar for Hg, In and all measured alloys, the electrical resistivity and thermoelectric power were evaluated using the random model and ANIMALU and HEINE pseudopotentials. The predicted resistivity was found to increase from 30µΩcm for pure Hg to 43 µΩcm for 35 atomic per cent In alloy and then to decrease to 24 µΩcm for pure In. The measured values of the resistivity decrease from 96 µΩcm for Hg to 30 µΩcm for pure In. Beyond the first eutectic composition, i. e., about 35 atomic per cent In concentration, the predicted resistivity curve decreases similarly to the measured resistivity curve. The discrepancy is attributed to the low density of states for Hg at the FERMI level. The predicted thermoelectric power decreases gradually from 1.22 µV/°K for pure Hg to 0.23 µV/°K for 62 atomic per cent In alloy, the value for pure In being 0.59 µV/°K. The measured values of thermoelectric power at 100°C decrease first from -6.5 µV/°K for pure Hg to -7.1 µV/°K for 5 atomic per cent In alloy and then increase to -0.7µV/°K for pure In. The discrepancy in the predicted values has been attributed to the energy dependence term of the pseudopotentials near the FERMI surface, particularly for pure Hg.