Energy bands and electron densities of Li3N

Self-consistent band-structure calculations on the fast ionic conductor lithium nitride are performed by means of the linearized augmented plane wave (LAPW) method within the local density formalism. The corresponding density of states is decomposed into local (inside spheres), partial (l-like) and symmetry (p x p y ;p z ) components from which an only very small covalent contribution to the bonding in Li3N can be deduced. Electron density maps reveal Li3N to be highly ionic (near Li+ and N3−). A simple Watson model, although a good first approximation, cannot account for all details. For instance a remarkable non-spherical electrons density is found around N which may explain the high electric field gradient experimentally observed on this site; furthermore a reduced electron density around the Li-sites appears in contrast to a simple supper-possition of N3− ionic densities. However, calculated x-ray structure factors and difference electron densities are in good qualitative agreement with recent x-ray diffraction experiments.