It's All in the (Cyanamide) Tilt: Synthesis and Structure of NaSc(NCN)2

Abstract

The ternary cyanamide NaSc(NCN)2 was prepared by a solid-state metathesis reaction between Na2NCN and ScCl3 at 600 °C. The orthorhombic crystal structure was determined from powder X-ray diffraction data to be isotypic to that of LiY(NCN)2 with Pbcn symmetry. As such the structure of NaSc(NCN)2 is well thought of as being derived from [NiAs]-type MNCN binaries with a hexagonally close-packed array of NCN2–. In this hettotypic form, however, the Na+ and Sc3+ cations occupy the octahedral holes in a 1:1 ordered fashion forming corrugated rows within the octahedral planes that alternate along the stacking direction. Furthermore, the significant cation size differential induces a pronounced tilting of the cyanamide anion away from the [100] direction. Electronic structure calculations indicate an indirect band gap of 3.41 eV (SCAN functional), in broad agreement with the measured value of 4.19 eV, which characterizes NaSc(NCN)2 as a wide-band-gap semiconductor.