Band structure and properties of polymorphic modifications of lower tungsten carbide W2C

The structural and electronic properties are investigated and the relative stabilities of all the known polymorphic modifications (alpha, beta, gamma, epsilon) of the lower tungsten carbide W2C are numerically estimated using the ab initio full-potential linearized augmented plane wave (FLAPW) method within the generalized gradient approximation (GGA) of the local spin density. The equilibrium parameters of the crystal lattices, the band structures, and the total and partial densities of states are determined for the first time within a unified approach. The energies of formation of the alpha, beta, gamma, and epsilon polymorphic modifications of the lower tungsten carbide [in the reactions W2C <-> 2W + C (graphite)] are calculated and used to discuss their relative stabilities.