Synthesis of novel chromium carbide using laser heated diamond anvil cell

High pressure-high temperature (HPHT) synthesis of a new phase of chromium carbide has been carried out using laser heated diamond anvil cell (LHDAC) at about 5 GPa and 1500 K. The reproducibility of the formation has been confirmed. The HPHT synthesized phase was retrieved to ambient condition and characterized by X-ray diffraction and micro-Raman spectroscopy. Various candidate structures obtained from experimental analysis have been evaluated by carrying out ab initio electronic structure calculations and the phase was identified to be an off-stoichiometric CrC which crystallizes in hexagonal lattice with space group (S. G.) P-6m2 (187). The lattice parameters of CrC were found out to be a = 2.7496(2) angstrom, c = 8.7010(4) angstrom and the bulk modulus was estimated to be 269 GPa. Study of density of states, band structure and charge density distribution indicate that CrC is metallic owing to the Cr-Cr metal bonds and there exists a p-d hybridization between the carbon and chromium electrons. The Cr-C bonds show covalent nature.