A new mixed group 5 metal selenide, Nb1.41V0.59Se9

Abstract

The new mixed-metallic phase, niobium vanadium nonaselenide, (Nb2-xVx)Se9 (0.18≤ x ≤ 0.59) is isostructural with monoclinic V2Se9. The structure is composed of chains of bicapped trigonal–prismatic [MSe8] units. The metal (M) site is occupied by statistically disordered Nb [0.706 (5)] and V [0.294 (5)] atoms. Two trigonal prisms are linked by sharing a rectangular face composed of two Se22− pairs. Through three edging and capping Se atoms, the chains are extended along [101]. The chain shows alternating short [2.8847 (7) Å] and long [3.7159 (7) Å] M—M distances. The structure shows a wide range of Se—Se interactions. In addition to the Se22− pairs of the rectangular face, an intermediate Se...Se separation [2.6584 (5) Å] is found. The amount of each metal can vary, [(Nb2-xVx)Se9, 0.18 ≤ x ≤m 0.59] and they seem to form a random substitutional solid solution. The M—M distances increase gradually by increasing the amount of Nb atoms. The classical charge-balance of the compound can be described as [M4+]2[Se22−]2[Se54−].