Electronic and Structural Properties of the Liquid (Tl_1/2Pb_1/2)‐Se System

The electrical conductivity, magnetic susceptibility, and thermoelectric power in the liquid (Tl_1/2Pb_1/2) Se system are measured over wide temperature and composition ranges. It is observed that the electrical conductivity in the system sharply falls near the stoichiometric composition of Tl₂Pb₂Se₃ and the magnetic susceptibility has a diamagnetic maximum at this composition, where the thermoelectric power changes its sign. In addition, the DTA investigation shows that the liquidus temperature of the system has a maximum around this composition. These results suggest that a short‐range order appears around the composition of Tl₂Pb₂Se₃ in the liquid (Tl_1/2Pb_1/2)‐Se system. The delocalized electron analysis using both susceptibility and conductivity data suggests that the bonding nature of liquid Ti₂Pb₂Se₃ is rather ionic. The radial distribution study by neutron diffraction also exhibits that the first peak position of g(r) for liquid Tl₂Pb₂Se₃ is located near the ionic bond distance of metal and chalcogen atoms. On the other hand, covalent Se‐ Se bonds are formed in the Se‐rich composition range.