Nickel – p-block metal mixed chalcogenides based on AuCu₃-type fragments: iodine-assisted synthesis as a way of obtaining new structures

Abstract

Two new mixed nickel-gallium chalcogenides, Ni9.39Ga2S2, Ni5.80GaTe2, and a new mixed nickel-indium telluride, Ni5.78InTe2, have been synthesized by a high-temperature ampoule route with an addition of iodine, and characterized from...

Role of Partial Vacancy and Structural Distortion in the Stability of Nonstoichiometric Phases Ni7−δInSe2–xSx (1.26 ≥ δ ≥ 0.94; 0 ≤ x ≤ 1.33)

“…139) space group, with Z = 2 (Figure S1). − In their general formula, Ni 7– δ ECh 2 , the stoichiometric index “7” represents the hypothetical full occupancy of the sites, while the symbol “ δ ” indicates the deviation from this full occupancy in the actual composition. The crystal structure of these intergrowth compounds Ni 7– δ ECh 2 consists of two type of slabs ( ∞ 2 [ Ni 3 E ] and ∞ 2 [ Ni 4−δ Ch 2 ]) alternating along the c -axis of the tetragonal unit cell.…”

“…26,32,33 The tellurium-containing compound shows a small degree of orthorhombic distortion with respect to the idealized tetragonal structure. 30 Hence, motivated by the fascinating structural features related to the family of intergrowth structures presented, the aim was to explore the Ni−In−S phase starting from Ni 7−δ InSe 2 through the gradual substitution of selenium by sulfur. Herein, we report the crystal structure and stability of a series of sulfur-substituted compounds, Ni 7−δ InSe 2−x S x , through single-crystal X-ray diffraction analysis, powder X-ray diffraction (PXRD) analysis, and first-principles theoretical calculations.…”

“…In the sulfide compounds, Ni 7– δ E S 2 ( E = Sn, Ga, Ge, Al), ,− , the ∞ 2 [ Ni 4−δ Ch 2 ] slab is heavily disordered and accommodates an additional partially occupied Ni site. Hence, the atomic arrangement in the disordered ∞ 2 [ Ni 4−δ Ch 2 ] slab can either be built up by a defective Cu 2 Sb-type unit (common for Ni-based selenides and tellurides) ,− ,− or antifluorite Li 2 O/Cu 2 Sb-type structural unit (for Ni-based sulfides). ,− , Remarkably, the sulfur derivatives Ni 7– δ E S 2 (with same E ) in this family display a higher Ni-occupancy compared to selenium and tellurium derivatives. , These characteristic features have been noticed in this family of non-stoichiometric compounds, but no thorough investigation has been undertaken to rationalize these existing features. In particular, the role of such an optimal Ni-vacancy on the stability of this family of intergrowth structures is still unclear, though it is stated that the geometry matching of two building units requires partially vacate Ni-position in the Ni– Ch fragments to avoid overly short Ni–Ni distances.…”

“…Herein, Ni 7– δ In Ch 2 has been chosen as a representative of this class of compounds for investigation. In Ni 7– δ In Ch 2 , mixed nickel–indium discerns such compounds with selenium and tellurium (Ni 5.74 InSe 2 and Ni 5.78 InTe 2 ), , whereas the sulfur compound is absent to date. The indium-containing compounds are one-way unique, as they stabilize the cuboctahedral building unit [ In@12Ni ], which adopts the Cu 3 Au-type at high pressure. ,, The tellurium-containing compound shows a small degree of orthorhombic distortion with respect to the idealized tetragonal structure …”