Novel pathways to nitridophosphate networks

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The project focuses on a synergistic approach toward the synthesis and structural analysis of (oxo)nitridophosphate network structures and variants thereof. Typically, new compounds are discovered as microcrystalline side phases in heterogeneous products of explorative syntheses. Electron crystallography and synchrotron microfocus diffraction help for their identification. Intermediate compounds are characterized in the same way and hint at reaction pathways. Based on this, syntheses are optimized aiming at phase pure products. Both the extension of (oxo)nitridophosphate structural chemistry as well as the elucidation of their mechanisms of formation in solid-state reactions under extreme conditions are targeted. Explorative high-temperature and high-pressure syntheses, precursor routes and their combinations are the starting point of this project. Reactions with the multianvil method are also examined with regard to the role of the mineralizing agents used therein. Beyond this, mixed nitridophosphate-silicates are to be synthesized and characterized as well. In addition to nitridation and metathesis reactions, pre-organized molecular precursor routes represent a promising approach. The crystallization behavior of intermediately formed nitride glasses will be investigated. Metastable microcrystalline phases can be used as precursors leading to novel nitride networks. The project further focuses on characterizing high-pressure phases of (oxo)nitridophosphates and PON itself. Heterogeneous products and minority phases are to be identified by electron crystallography and are structurally characterized. Powerful methods such as electron diffraction tomography and the combination of TEM and X-ray diffraction with synchrotron radiation are employed for precise structure determination of micro- to nano-crystalline compounds. Complex nitride structures frequently exhibit real-structure effects which are analyzed using STEM-HAADF, high-resolution EDX and EELS mapping as well as the characterization of diffuse scattering. The characterization of trapped intermediates provides essential information concerning the understanding of formation mechanisms. Thus, synthetic routes can be optimized to obtain phase pure products. Their potential properties such as ionic conductivity or zeolite-like behavior will be examined in cooperation. In addition, theoretical calculations (DFT) of particularly interesting nitride structures are planned. In conclusion, this project will efficiently combine ambitious syntheses with modern methods of structural analysis in order to identify and access challenging nitride network structures.