Preparation, crystal structure and electrical properties of Cu4SnS6

Single crystals of Cu4SnS6 were grown in an eutectic flux of 54% KCl and 46 % LiCl. The X-ray crystal structure analysis showed that Cu4SnS6 crystalliz es in a new layered structure with rhombohedral symmetry: R (3) over bar m, a = 3.739(1), c = 32.941(7) Angstrom, Z = 2, R = 0.037 for 188 reflections and 18 variables. The crystal structure comprises structural slabs of four sulfur layers. Three of those slabs are stacked rhombohedrally along the c axis and connected by S-S bonds to build the unit cell. 0.661(6) Sn and 0. 326(6) Cu atoms are statistically distributed over the octahedral voids, wi th the Cu atoms moving toward two opposite triangular sulfur faces, and pes t of the Cu atoms in Cu4SnS6 occupy the tetrahedral holes. The overall laye r sequence is B alpha AcB beta A\A gamma CbA alpha C\C beta BaC gamma B. El ectrical conductivity measurements indicate that Cu4SnS6 might be metallic. (C) 1999 Elsevier Science Ltd.