X-RAY STUDY OF THE ROOM-TEMPERATURE STRUCTURE IN MONOCLINIC TLS

TlS is known as a mixed valence compound containing monovalent and tri valent thallium ions. The structure of the newly found monoclinic TlS has been analyzed using three-dimensional single crystal diffraction d ata. Space group C2: a=11.018(6), b=11.039(15), c=60.16(7) angstrom, b eta=100.69-degrees(4) and Z=128. The structure is characterized by lay ers formed of corner-connected Tl+3S4 tetrahedra. Monovalent Tl1+ ions are located between the layers and have trigonal prismatic coordinati on of the sulfur ions. The structure is a variation of the TIGaSe2 typ e with fourfold modulation along the c-axis. The modulation is caused by cooperative distortion of trigonal prisms around the monovalent Tl1 + ions.