An ab initio study of the energetics for interfaces between group V transition metal carbides and bcc iron

An ab initio study was carried out on interface energies, misfit strain energies, and electron structures at coherent interfaces between bcc Fe and MCs (NaCl structure, M=V, Nb, Ta). The interface energies at relaxed interfaces Fe/VC, Fe/NbC, and Fe/TaC were -0.120, -0.169 and -0.158 J/m(2), respectively. Influence of bond energy was estimated using the discrete lattice plane/nearest neighbor broken bond (DLP/NNBB) model. It was found that the dependence of interface energy on the type of carbide was closely related to changes of the bond energies between Fe, M and C atoms before and after formation of the interfaces Fe/MC. The misfit strain energies in Fe/VC, Fe/NbC, and Fe/TaC systems were 0.086, 0.891 and 0.827 eV per 16 atoms (Fe; 8 atoms and MC; 8 atoms), respectively. The misfit strain energy became larger when difference of lattice parameters between the bulk Fe and the bulk MCs increased.