Synthesis, structure, and electrical properties of Eu 0.59Nb 5Se 8

Abstract

The new compound Eu 0.59Nb 5Se 8 has been prepared from a combination of the elemental powders at 1275 K. The material crystallizes with four formula units in space group C 3 2h- C2 m of the monoclinic system in a cell (at 113 K) of dimensions a = 17.95(2), b = 3.388(4), c = 19.30(2)Å, β = 107.90(2)°. The structure has been solved and refined from single-crystal X-ray data. The asymmetric unit contains two independent Eu atoms, five independent Nb atoms, and eight independent Se atoms. Each Eu site is approximately 59% occupied; the Eu atoms are in an unusual distorted cube of Se atoms with EuSe interactions ranging from 3.108(6) to 3.454(6) Å. Three of the independent Nb atoms are in trigonal prisms of Se atoms with NbSe interactions ranging from 2.548(6) to 2.617(6) Å while the other two independent Nb atoms are in unusual distorted octahedral environments with NbSe interactions ranging from 2.526(9) to 2.718(7) Å. These latter two Nb atoms show short NbNb interactions of about 2.95 Å. The material exhibits excellent metallic conductivity along the needle ( b) direction with σ 298 K of 35 × 10 3 ohm −1 cm −1 and σ 12 K ≈ 1.4 × 10 6ohm −1 cm −1.