Physical Properties and Electronic Structure of Ternary Barium Copper Sulfides

Thiocuprates—Interesting anisotropic solids

“…According to the already mentioned observation that one cationic charge per ideal formula unit is missing in all known mixed-valent compounds, there should also be one hole per formula unit in the valence band. An extended Hückel calculation for ␤-BaCu 2 S 2 corroborated the mainly ionic character of the bonding between barium and the [Cu 2 S 2 ] layers and the predominantly covalent bonding between copper and sulphur [62].…”

“…Most of the normal valent compounds are semiconducting and diamagnetic [61][62][63]. A paramagnetic increase of the susceptibilities at low temperatures is assigned to traces of paramagnetic impurities.…”

An experimental study on the preparation of tochilinite-originated intercalation compounds comprised of Fe1−xS host layers and various kinds of guest layers

“…The iron sulfide layer in stoichiometric mackinawite (Lennie et al, 1995a;Rickard et al, 2006) has almost the same structure as those of the anionic layers of stoichiometric ThCr 2 Si 2 -type chalcogenides (Klepp and Boller, 1978;Berger, 1989;Ouammou et al, 1995;Oledzka et al, 1996;Llanos et al, 1996;Zhang et al, 1996). The iron sulfide layers in tochilinite do not have the ideal mackinawite structure; instead they have chessboard-like structures with Fe-vacancies populated in the sulfur tetrahedron interstices, which results in Fe-deficiency in the iron sulfide layers (i.e., Fe 1Àx S layers; Organova et al, 1974).…”

“…The typical electronic property of the ThCr 2 Si 2 -type chalcogenide layers (e.g., M 2 X 2 layers with M = Cu, Co, Fe, and T = S, Se) is that they can be both metallic hole-conductors (i.e., p-type conductors) and semiconductors depending on the presence or absence of holes in the valence bands (Berger andVan Bruggen, 1984, 1985;Berger, 1989;Karlsson et al, 1990;Ouammou et al, 1995;Zhang et al, 1996;Tiedje et al, 2003;Ronneteg et al, 2004;Yablonskikh et al, 2006). The upper valence bands of the ThCr 2 Si 2 -type chalcogenide layers are mainly made up of the p states of the chalcogen atoms.…”

Electrical and Magnetic Properties of New Mixed Transition Metal Sulfides BaKCu3MS4 (M=Mn, Co, Ni)

“…The di!erence has been attributed to the presence of a certain amount of Cu> (d) in Ba K Cu S while copper ions are monovalent Cu> (d) in BaCu S (7,8). We decided to investigate structurally related systems in which a larger concentration of copper ions has been replaced by nonisoelectronic transition elements.…”