Discovery of Two Polymorphs of TiP4N8Synthesized from Binary Nitrides

Abstract

AbstractTiP4N8was obtained from the binary nitrides TiN and P3N5upon addition of NH4F as a mineralizer at 8 GPa and 1400 °C. An intricate interplay of disorder and polymorphism was elucidated by in situ temperature‐dependent single‐crystal X‐ray diffraction, STEM‐HAADF, and the investigation of annealed samples. This revealed two polymorphs, which consist of dense networks of PN4tetrahedra (degree of condensationκ=0.5) and either augmented triangular TiN7prisms or triangular TiN6prisms for α‐ and β‐TiP4N8, respectively. The structures of TiP4N8exhibit body‐centered tetragonal (bct) framework topology. DFT calculations confirm the measured band gaps of α‐ and β‐TiP4N8(1.6–1.8 eV) and predict the thermochemistry of the polymorphs in agreement with the experiments.