Effect of impurities on the growth and morphology of cementite nanowires.

The effects of doping on the morphology of iron carbide (cementite) nanowires have been explored by first principles electronic structure calculations. We examined the role of several realistic impurities (Si, Mn, V, P and S) in the formation energies of cementite nanowires with different sizes and morphologies. It is shown that the presence of the impurities decreases the formation energy and can switch the preferable axis of the cementite nanowire growth. The conditions of the formation and decomposition of cementite nanowires in steels are also discussed.