Dicalcium nitride, Ca2N - a 2D "excess electron" compound; synthetic routes and crystal chemistry

The subnitride Ca2N has been prepared via several synthetic routes describe d for the first time, including reduction of Ca3N2 and reaction of Ca metal dissolved in liquid sodium with nitrogen gas. Products have been character ised by powder X-ray and powder neutron diffraction. Crystallite morphology and compound stoichiometry have been examined by SEM/EDAX. Ca2N crystallis es with a hexagonal layered structure in space group <R(3)over bar>m (a = 3 .62872(3) Angstrom, c = 19.0921(4) Angstrom, V = 217.72(1) Angstrom(3), Z = 3, c/a = 5.26). [NCa2](+) layers composed of compressed, edge-sharing NCa6 octahedra stack along the c-axis and are separated by large "van der Waals " gaps. The material is metallic and paramagnetic at room temperature. The c-parameter, [NCa2](+) layer thickness and interlayer gap are larger than p reviously reported and there is no evidence of hydride or other anion inter calation between layers.