Synthesis,crystal structure,and physical properties of a new boride Ga2Ni21B20 with a modified Zn2Ni21B20-type structure

A ternary boride Ga₂Ni₂₁B₂₀, with modified Zn₂Ni₂₁B₂₀-type structure (space group I4/mmm, and lattice parameters a = 7.2164(1) Å, c = 14.2715(4) Å), was synthesized from the constituent elements. Single crystal diffraction data reveal Ni at 8f site splitting into 16m position with nearly half occupancy. In this structure, Ni₆B₂₀] cages share ligand boron atoms with Ga₂B₄Ni₉] hexa-capped square prisms, forming two dimensional layers. Layers are interconnected via Ga−Ni interactions and build up a three-dimensional framework. Quasi-two-dimensional infinite planar nets formed by intercrossed Ni atoms are embedded. Ga₂Ni₂₁B₂₀ is a metallic Pauli paramagnet, in agreement with electronic structure calculations, resulting in 8.2 states eV⁻¹ f.u⁻¹ at the Fermi level.