The occupation and migration of boron (B) and carbon (C) in both body-centered cubic (BCC) iron and face-centered cubic (FCC) iron have been investigated using first-principles calculations. We examined the solution energies of all potential sites, including substitution sites (SS), octahedral sites (OIS) and tetrahedral sites (TIS) for B and C in BCC and FCC Fe. The site’s preference of an individual B/C atom in iron forms the following sequence: SSFormula: see text Formula: see text Formula: see textTISFormula: see text Formula: see text Formula: see textOIS, for a B atom in BCC Fe; SSFormula: see text Formula: see text Formula: see textOISFormula: see text Formula: see text Formula: see textTIS, for a B atom in FCC Fe; OISFormula: see text Formula: see text Formula: see textTISFormula: see text Formula: see text Formula: see textSS, for a C atom in BCC and FCC Fe. The optimal migration paths and the minimum diffusion energy barrier of B and C in both BCC and FCC iron have also been investigated. The migration path sequences are as follows: Tet 1 –Tet 2 and Oct 1 –Oct 2 for boron in BCC and FCC iron; Oct 1 –Tet–Oct 2 and Oct 1 –Oct 2 for carbon in BCC and FCC iron. The diffusion energy barriers are 0.87Formula: see texteV and 0.98Formula: see texteV for carbon and 0.89Formula: see texteV and 1.02Formula: see texteV for boron in BCC and FCC Fe. We found that much more energy is needed for B and C migrating in FCC Fe.
Liu et al. (Wed,) studied this question.