Potential existence of postperovskite nitrofluorides: In silico LaZrN2F

Based on the ionic versus covalent bonding mismatch in nitrofluorides and on the distorted edge sharing octahedra in postperovskite (ppv) structure of known oxides, we propose the potential existence of ppv nitrofluorides from first principles in the framework of the density functional theory. For an archetype LaZrN2F composition, the equations of state for GdFeO3-distorted perovskite (o-pv) and postperovskite (ppv) forms are computed. The ppv form is found stabilized at lower volume with a higher hardness than o-pv. From energy differences with respect to LaN and ZrNF precursors, a negative formation energy characterizes ppv contrary to o-pv which is computed with a positive energy. This lets suggest a high pressure helped synthetic conditions which are proposed herein. The electronic band structure shows semi-conducting properties with iono-covalent behavior.