  The electronic band structures along with Fermi surface, anisotropy, Vickers
hardness, analysis of Mulliken populations, optical and thermodynamic
properties were studied for the first time. The optimized unit cell parameters
are compared with available theoretical and experimental results and a
reasonable agreement is recorded. The mechanical stability of these compounds
is confirmed. All the compounds herein exhibit metallic conductivity where
major contribution comes from d-orbital electrons. The hardness values of
10.71, 12.44, 8.52 and 16.80 GPa were recorded for M2BC (M = V, Nb, Mo and Ta)
compounds, respectively. The value of bulk modulus, B is found to increase in
the sequence B (V2BC) < B (Nb2BC) < B (Ta2BC) < B (Mo2BC), indicates Mo2BC is
highly stiff among all compounds. The Mo2BC and Ta2BC compound might be
considered as potential candidates for protection of cutting and forming tools
due to the moderately ductile and highly stiff behavior compared to other
benchmark hard coating materials such as TiN, TiAlN, Ti0.5Al0.5N and c-BN.
Ta2BC compound could also be a promising thermal barrier coating (TBC) material
due to the reasonable results of minimum thermal conductivity, Debye
temperature and damage tolerance behavior. Various optical functions such as
dielectric constants, refractive index, photo-conductivity, absorption, loss
function and reflectivity) are calculated and discussed in details. The amount
of reflectivity was always more than around 50% with no significant change in
the near infrared, visible light and near ultraviolet region (up to ~6 eV),
which results a promising coating material to diminish solar heating as well.
