Structural, magnetic, and optical properties of nano‐sized Ni_0.85Se

Abstract

Nanocrystalline Ni 0.85 Se was synthesized by a hydrothermal method. X-ray diffraction analysis by Rietveld method indicated that Ni 0.85 Se has a NiAs-type hexagonal structure. Narrow crystallite size distribution with an average areaweighted size of 〈ɛ F 〉 = 8.5 nm is obtained by Warren-Averbach method. Structural analysis revealed deformed Se atoms octahedron with the shortest distance between Se atoms in adjacent planes 〈Se-Se〉 adj smaller than between nearest neighbors in layer plane 〈Se-Se〉 nea , and a rather short interatomic distance between the transition metal atoms 〈Ni-Ni〉. The optical property of Ni 0.85 Se was studied by UV-spectroscopy. Magnetic measurement shows a ferromagnetic phase transition for Ni 0.85 Se below 14 K. K E Y W O R D Schalcogenides, magnetic properties, microstructure, nanostructures, UV

Investigation of the potassium‐ion storage mechanism of nickel selenide materials and rational design of nickel selenide‐C yolk‐shell structure for enhancing electrochemical properties

“…Rietveld refinement was carried out using a cubic structure in the Pa-3 space group with cell parameters of a = b = c = 5.9612 (6) Å and α = β = γ = 90 for the NiSe 2 and hexagonal structure in the P 63/mmc space group with cell parameters of a = b = 3.5906 (4), c = 5.2686 (6) Å, α = β = 90 , and γ = 120 for the Ni 0.85 Se phase. 24,25 The phase fractions of NiSe 2 and Ni 0.85 Se were calculated to be $85.0 and $15.0 mol%, respectively. The energy-dispersive Xray spectroscopy (EDS) mapping images displayed in Figure 1E indicate the uniform composition of the nanocrystals with nickel and selenium elements.…”

Ce-Doped NiSe Nanosheets on Carbon Cloth for Electrochemical Water-Splitting

“…25−27 The crystal structure for the hexagonal P6 3 /mmc phase (space group no. 194) of the Ni 0.85 Se compound, as obtained from experimentally determined X-ray powder diffraction data under ambient condition (P = 0 GPa, T = 300 K), 28 has been initially optimized using "variable-cell relaxation" method followed by the Broyden−Fletcher−Goldfarb−Shanno scheme. 29−32 The projector augmented wave (PAW) pseudopotential 33 has been included to consider the electron−ion interactions.…”

“…The lattice parameters of the crystal system under study have been estimated to be a = b = 3.634 Å and c = 5.333 Å, which are in close agreement with the experimentally determined Xray powder diffraction data reported elsewhere. 28 To introspect the structural stabilities of 5% 8a and b, respectively. From Figure 8a, the top of the valence band edges and bottom of the conduction band edges of the Ni 0.85 Se compound are observed at Γ, M, and Γ, K high symmetry points, respectively, in the Brillouin zone.…”

Recent Progress and Prospective of Nickel Selenide-Based Electrocatalysts for Water Splitting

“…Therefore, the study of their crystal structure is of great significance for understanding the performance of these catalysts. The crystal structure and stoichiometric changes of Ni/Se have great influence on their catalytic performance. − For example, Zheng et al synthesized Ni x Se (0.5 ≤ x ≤ 1) nanocrystals with precise phase and composition control, such as pure hexagonal NiSe, Ni 0.85 Se, monoclinic Ni 3 Se 4 , and cubic NiSe 2 phases . Se atoms are arranged in a hexagonal dense structure, and Ni atoms are filled in the octahedral holes.…”