RADIAL-DISTRIBUTION STUDIES OF TL-S ALLOYS IN LIQUID AND AMORPHOUS STATES

Neutron diffraction measurements in liquid TlxS1-x alloys with x = 0.6 7, 0.57, 0.50, 0.33 and 0.29 have been carried out to obtain their sho rt-range structures. For the comparison, the amorphous structure of th e alloys with 0.50 greater than or equal to x greater than or equal to 0.29 has been investigated also through X-ray diffraction measurement s. The liquid alloy has a chemical order relating to the crystalline p hase at x = 0.67 (corresponding to the composition of Tl2S), where the metal-nonmetal transition occurs. The liquid structure at the rest fo ur compositions is considerably different from the corresponding cryst alline one. Consequently, two distinct chemical orders appear in the c omposition range between Tl2S and S in the liquid state, i.e., the Tl2 S-like chemical order and sulfur linkage unit. On the other hand, crys talline chemical orders are rather retained in the amorphous state, fo r example, TlS4/2 tetrahedra in crystalline TlS and Tl2S5 molecular un its in crystalline Tl2S5 has been observed also in the amorphous state .