  Theoretical investigation of structural, elastic, electronic and bonding
properties of A-15 Nb-based intermetallic compounds Nb3B (B = Pt, Os) have been
performed using first principles calculations based on the density functional
theory (DFT). Optimized cell parameters are found to be in good agreement with
available experimental and theoretical results. The elastic constants at zero
pressure and temperature are calculated and the anisotropic behaviors of the
compounds are studied. Both the compounds are mechanically stable and ductile
in nature. Other elastic properties such as Pugh's ratio, Cauchy pressure,
machinability index are derived for the first time. Nb3Os is expected to have
good lubricating properties compared to Nb3Pt. The electronic band structure
and energy density of states (DOS) have been studied with and without
spin-orbit coupling (SOC). The band structures of both the compounds are spin
symmetric. Electronic band structure and DOS reveal that both the compounds are
metallic and the conductivity mainly arise from the Nb 4d states. The Fermi
surface features have been studied for the first time. The Fermi surfaces of
Nb3B contain both hole- and electron-like sheets which change as one replaces
Pt with Os. The electronic charge density distribution shows that Nb3Pt and
Nb3Os both have a mixture of ionic and covalent bonding. The charge transfer
between atomic species in these compounds has been explained by the Mulliken
bond population analysis.
