Nitridochromate(IV) fluoride - LiCa8[CrN3]2N2F

Abstract

LiCa₈[Cr^IVN₃]₂N₂F (Pnnm (#58), a = 17.5230(13) Å, b = 7.3379(5) Å, c = 4.9433(4) Å) is an example of a multinary nitridochromate fluoride, that provides additional information on almost elusive tetravalent nitridochromates. Shorter Cr-N bond lengths compared to those in the previously reported nitridochromates(III), as well as diamagnetic behavior and vibrational spectroscopy data suggest Cr(IV), which is in good agreement with the charge balance and crystal structure refinement. According to band structure calculations, LiCa₈[Cr^IVN₃]₂N₂F is a semiconductor with a band gap of 1.1 eV. The compound features trigonal planar [CrN₃]^5- units of C_s symmetry, and lithium, calcium, nitrogen and fluorine atoms arranged in a fragment of the rock salt type structure.