  Binary carbides demonstrate attractive set of physical properties that are
suitable for numerous and diverse applications. In the present study, we have
explored the structural properties, electronic structures, elastic constants,
acoustic behaviors, phonon dispersions, optical properties, and various
thermophysical properties of binary orthogonal and hexagonal Mo2C compounds in
details via first-principles calculations using the density functional theory
(DFT). The calculated ground state lattice parameters in both the symmetries
are in excellent agreement with available experimental results. The calculated
electronic band structure, density of states, and optical properties of Mo2C in
both structures reveal metallic features. The orthorhombic crystal shows higher
level mechanical and thermal anisotropy compared to that in the hexagonal
phase. The elastic constants and phonon dispersion calculations show that, in
both structures, Mo2C is mechanically and dynamically stable. A comprehensive
mechanical and thermophysical study shows that both phases possess high
structural stability, reasonably good machinability, ductile nature, high
hardness, low compressibility, high Debye temperature and high melting
temperature. Moreover, the electronic energy density of states, electron
density distribution, elastic properties, and Mulliken bond population analyses
indicate that the structures under consideration consist of mixed bonding
characteristics with ionic and covalent contributions. High reflectivity over
wide spectral range makes the compound suitable as reflecting coating. Both the
structures are efficient absorber of ultraviolet radiation. The refractive
indices are quite high in the infrared to visible range.
