Synthesis of a cubic Ge3N4 phase at high pressures and temperatures

The two known phases of germanium nitride (Ge3N4) have hexagonal and trigonal symmetries and consist of three-dimensional networks of corner-connected Ge-N tetrahedra. A new cubic spinel phase (space-group Fd3m, a(0)=8.3 Angstrom, Z=8, rho=6.36 g/cm(3)) containing Ge-N octahedra and tetrahedra in a 2:1 ratio was synthesized from elemental germanium and molecular nitrogen starting materials in a laser-heated diamond-anvil cell above 14 GPa. This phase is isostructural to the recently discovered cubic spinel phase of Si3N4. (C) 1999 American Institute of Physics. [S0021-9606(99)51634-6].