Electronic Structure Properties of Nickel Carbides

Our analyses of nickel carbides have shown that hexagonal Ni$_{3}$C ($\Delta $E = 6.4 kcal/mol) is more stable than NiC ($\Delta $E = 48.6 kcal/mol). To understand the change in stability between these nickel carbides, we have examined the electronic stability and structure of Ni$_{2}$C. Using the Vienna Ab-initio Simulation Package (VASP) code, the most stable ground state arrangement of Ni$_{2}$C was determined. The total density of states of Ni$_{2}$C, the density of states for each nickel and carbon atom within the primitive lattice, and the band structure of Ni$_{2}$C were examined. The electronic structure of Ni$_{2}$C was compared to those of diamond, NiC (rock salt), and Ni$_{3}$C (hexagonal). For Ni$_{2}$C, the Fermi energy was obtained and the behavior of the band structure around the Fermi energy was classified. The density of states for nickel and carbon within the relaxed lattice were used to understand the bonding mechanism that exists within Ni$_{2}$C.