Synthesis and Comprehensive Studies of Be-IV-N (IV=Si, Ge): Solving the Mystery of Wurtzite-Type Pmc2 Structures.

The research for wurtzite-type ternary nitride semiconductors containing earth abundant elements with a stoichiometry of 1 : 1 : 2 was focused on metals like Mg or Zn, so far. The vast majority of these Grimm-Sommerfeld analogue compounds crystallize in the β-NaFeO structure, although a second arrangement in space group Pmc2 is predicted to be a viable alternative. Despite extensive theoretical and experimental studies, this structure has so far remained undiscovered. Herein, we report on BeGeN in a Pmc2 structure, synthesized from BeN and GeN using a high-pressure high-temperature approach at 6 GPa and 800 °C. The compound was characterized by powder X-ray diffraction (PXRD), solid state nuclear magnetic resonance (NMR), Raman and energy dispersive X-ray (EDX) spectroscopy, temperature-dependent PXRD, second harmonic generation (SHG) and UV/Vis measurements and in addition also compared to its lighter homologue BeSiN in all mentioned analytic techniques. The synthesis and investigation of both the first beryllium germanium nitride and the first ternary wurtzite-type nitride crystallizing in space group Pmc2 open the door to a new field of research on wurtzite-type related structures.