The thermoelectric power of fluid mercury in the density range of the metal nonmetal transition

Abstract

AbstractThe absolute thermoelectric power of liquid and supercritical mercury has been measured between 600°C and 1700°C at pressures up to 3300 bar. For that purpose a cell of forged molybdenum and pure sintered alumina was developed which allows the simultaneous measurement of the thermoelectric power S and the electrical conductivity σ of liquid and gaseous mercury. The measurements were performed in an internally heated high pressure vessel.A strong density dependence of S and σ is observed. If the mercury density is decreased from 12 g/cm3 to 5 g/cm3, S varies continuously from ‐ 23 μV/deg to ‐ 550μV/deg indicating a gradual transition from a metallic to a nonmetallic state. It is proposed that a pseudogap is formed in expanded mercury and that the states in the pseudogap become localized for densities smaller than 9 g/cm3. For densities smaller than this σ and S are consistent with excitation of electrons from localized states at the fermi energy to extended states at the mobility edge.