A cubic phase of C3N4 synthesized in the diamond-anvil cell.

A cubic phase of C3N4 was discovered. It was recovered at ambient conditions from the graphite-like C3N4 (g-C3N4) phase subjected to pressures between 21 and 38 GPa in a diamond-anvil cell, laser heated to temperatures between 1600 and 3000 K. The x-ray-diffraction data of the phase are best explained by a cubic unit cell with the lattice parameters a=3.878±0.001 Å. With an assumption of 1 molecule/unit cell (Z=1) for the cubic phase, the molar volume of the cubic phase is 35.126 cm3/mol and the density is 2.62 g/cm3. The density of the cubic phase is less than that which was predicted for the high-pressure phases but is 12% denser than the low-pressure graphitic phase (ρ=2.336 g/cm3). The cubic phase has not been predicted theoretically and represents an unknown structure in C3N4. [ABSTRACT FROM AUTHOR]