The point defect structure of cementite (Fe3C) was investigated using a

combination of the statistical mechanical Wagner–Schottky model and firstprinciples

calculations within the generalized gradient approximation. Large 128-

atom super-cells were employed to obtain fully converged point defect formation energies. The present study unambiguously showed that carbon vacancies and

octahedral carbon interstitials were the structural defects in C-depleted and C-rich

cementite, respectively. The dominant thermal defects in C-depleted and

stoichiometric cementite were found to be carbon Frenkel pairs. In C-rich

cementite, however, the primary thermal excitations were strongly temperaturedependent:

interbranch, Schottky and Frenkel defects dominate successively with

increasing temperature. Using the nudged elastic band technique, the migration

barriers of major point defects in cementite were also determined and compared

with available experiments in the literature.

Point Defect Thermodynamics and Diffusion in Fe3C: a First-Principles Study.

C.Jiang, B.P.Uberuaga, S.G.Srinivasan: Acta Materialia, 2008, 56[13], 3236-44