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

Abstract

Abstract The 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/cm 3 to 5 g/cm 3 , 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/cm 3 . 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.