CHEMICAL SHORT-RANGE ORDER AND THE MEYER-NELDEL RULE FOR LIQUID ALLOYS - ALCA AND GAALCA

We have measured the electrical resistivity, rho, its specific tempera ture dependence, alpha = (1/rho)d rho/dT, and the thermopower, S, of t wo series of ternary liquid alloys: GaxAl67-xCa33 and GaxAl50-xCa50. W e also provide new analysis for the binary liquid alloy AlCa. We do no t see the unusually large values for S that were found earlier for amo rphous solid ternary alloys of the approximate composition GaxAlyCa60. We do find that, while chemical short-range order (CSRO) appears to o ccur in the liquid binary alloy Al2Ca, CSRO is apparently destroyed by substitution of one Ga atom for one Al per complex: Ga1Al1Ca1. CSRO m ay exist in the liquid alloy Ga2Ca. And we find that the activated con ductivities of these ternary liquid alloys (and also of liquid AlCa) a re consistent with the Meyer-Neldel rule (MNR), extending the range of applicability of the MNR to systems with activation energies about an order of magnitude smaller than previously observed. These results ap pear to rule out two physical models as universal bases for the MNR, b ut are consistent with one based on a hopping conductivity whose chara cteristic energy is that of a polaron shift.