Ni_5.73InSe₂– a Metal‐Rich Selenide Based on the Cu₃Au‐Type 2D Het­erometallic Framework: Synthesis, Structure, and Bonding

Abstract

A new metal‐rich nickel–indium selenide, Ni5.73InSe2, was synthesized by annealing a mixture of the elements with a 6:1:2 ratio at 650 °C for 7 days with subsequent cooling to room temperature. Its crystal structure was determined from single‐crystal diffraction data, and the composition confirmed by an EDS analysis. The compound crystallizes in the tetragonal system [I4/mmm, a = 3.6797(5) Å, c = 18.845(4) Å, Z = 2] and is isotypic with the Ni7–xMQ2 phases (M = Si, Ge, Sn, Sb; Q = S, Se, Te). Its main structural units are indium‐centered [Ni12In] cuboctahedra of the Cu3Au type and [Ni4–xSe2] blocks of the Cu2Sb type, alternating along the c axis. Electronic structure calculations on the DFT/FP‐LAPW level predict metallic properties and indicate a temperature‐independent paramagnetic behavior for the new compound, which is supported by the experimental measurements. The ELI‐D topological analysis shows the multi‐centered nature of the bonding in both the nickel–indium and nickel–selenium fragments. Ni5.73InSe2 represents the first example of a quasi‐2D mixed nickel–group 13 metal chalcogenide featuring [Ni12M] cuboctahedra of the Cu3Au type.

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) (Figure ). Up to x = 0.94, the structure is isostructural to their parent Ni 5.74 InSe 2 and therefore can be represented by 2D Cu 2 Sb-type Ni– Ch slabs of ∞ 2 [ Ni 4−δ Se 2–x S x ] and Cu 3 Au-type heterometallic slabs with composition ∞ 2 [ Ni 3 In ] stacking alternately along the c -axis by sharing their common square face (Figure a).…”

“…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.…”

“…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. Up to a sulfur content of x = 0.94, the non-stoichiometric compounds adopt the structure of the parent phase Ni 7– δ InSe 2 ( I 4/ mmm ). Above that sulfur content, an additional partially occupied nickel position emerges in close proximity to the existing nickel site in the structural model, and it resembles the Ni 6 SnS 2 -type structure.…”

The Zintl Concept Applied to Intergrowth Structures: Electron‐Hole Matching, Stacking Preferences, and Chemical Pressures in Pd5InAs

“…The transferability of these bonding schemes among the structures hints that analogous pictures can be drawn for other group 10 metalbased compounds. We are looking forward to seeing how similar bonding configurations may be used to unify the broader structural chemistry [13][14][15][16][17] of this family of intermetallic phases.…”

“…In this Article, we will consider the structure of Pd 5 InAs as an instance of such a situation, in which a preferred stacking arrangement reveals key bonding features. This compound represents a broader family of group 10 element-rich intermetallics incorporating AuCu 3 -type units [13][14][15][16][17] and has previously been explored for its potential to host hydrogen. [18] It adopts the Pd 5 TlAs structure type (Figure 1), [19][20][21] in which 1-unit-cell thick slabs of the AuCu 3 type and layers of edge-sharing filled square prisms derived from the PtHg 2 type [22] (or its stacking variant, the fluorite type) [23] alternate along the c direction.…”