Tetrahedrally bonded dense C2N3H with a defective wurtzite structure: X-ray diffraction and Raman scattering results at high pressure and ambient conditions

Abstract

Synchrotron x-ray diffraction and Raman scattering data supported by ab initio calculations are reported for the dense tetrahedrally bonded phase (C2 N3 H) with a defective wurtzite (dwur) structure synthesized by laser heating from dicyandiamide (C2 N4 H4) at high pressure in a diamond anvil cell. This work confirms the structure deduced in previous work from electron diffraction experiments. The phase (Cmc 21) is recoverable to ambient conditions. The ambient pressure volume (V0 =137.9 3) and bulk modulus (K0 =258±21GPa) are in excellent agreement with density functional calculations (V0 =134.7 3; K0 =270GPa). The calculated Raman frequencies and pressure shifts are also in good agreement with experiment. Ammonia (P 21 21 21) was identified among the reaction products as expected from the synthesis reaction. © 2009 The American Physical Society.