First examples of nickel–Aluminum mixed chalcogenides based on the AuCu3-type fragments: Breaking a robust intermetallic bond system in Ni3Al

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)

“…The crystal structure of these intergrowth compounds Ni 7−δ ECh 2 consists of two type of slabs Cu 2 Sb-type structural unit (for Ni-based sulfides). 22,[27][28][29]31 Remarkably, the sulfur derivatives Ni 7−δ ES 2 (with same E) in this family display a higher Ni-occupancy compared to selenium and tellurium derivatives. 29,31 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.…”

“…A similar impact on the geometry of [ In@12Ni ] unit is observed when moving along the S–Se–Te compounds in the structures of Ni 7– δ ECh 2 with the same “ E ” (Table S8). , As a consequence of the height contraction of the [ Ni 4−δ Ch 2 ] unit, the local coordination environment within it is also affected. For instance, the square pyramidal height of [ Ni1­(4e)@5Ch ] decreases (Figure b,c), and consequently, the Ni1 and Ch sites are brought into proximity to each other (Table and Figure c).…”

“…Up to x = 0.94, the structure is isostructural to their parent Ni 5.74 InSe 2 26 and therefore can be represented by 2D Cu S8). 29,31 As a consequence of the height contraction of the [Ni 4−δ Ch 2 ] unit, the local coordination environment within it is also affected. For instance, the square pyramidal height of [Ni1(4e)@5Ch] decreases (Figure 2b,c), and consequently, the Ni1 and Ch sites are brought into proximity to each other (Table 4 and Figure 2c).…”

“…In selenide- and telluride-based Ni 7– δ ECh 2 , the ∞ 2 [ Ni 4−δ Ch 2 ] slab is partly disordered and possesses partial occupancy at a Ni site. 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 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.…”