Synthesis of novel chromium carbide using laser heated diamond anvil cell

Abstract

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) Å, c ​= ​8.7010(4) Å 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.