www.elsevier.com/locate/suscwork was also performed on SGI2000 machines available at NC

We report a pseudopotential-based density functional theory (DFT) investigation of the interface between ZrC and bcc Fe. ZrC is a potential candidate for a protective coating for ferritic steels because of its favorable physical, chemical, and mechanical properties. Here we predict the atomic structure, bonding, and ideal work of adhesion ðW idealad Þ of the interface formed between the most stable surfaces of ZrC and bcc Fe, namely, the ZrC(1 0 0)/Fe(1 1 0) interface. Bulk properties of ZrC and bcc Fe, calculated for calibration of the DFT approximations involved, are in good agreement with experiment. Further, all the low-index surfaces of ZrC and bcc Fe are observed to retain near ideal bulk termi-nation, as observed experimentally. Stabilities of both ZrC and bcc Fe surfaces follow their respective packing density sequence, i.e., (1 1 0) < (1 1 1) < (1 0 0) for ZrC and (1 1 1) < (1 0 0) < (1 1 0) for bcc Fe. Based on surface energy values, we estimate that the critical stress required for crack propagation in bcc Fe to be at least 30 % larger than in ZrC. The ZrC(1 0 0)/Fe(1 1 0) interface is well lattice-matched (1.7 % strain) producing a fairly smooth interface with little structural relaxation. Bonding at the interface consists of covalent C p–Fe d mixing and some metallic Zr d–Fe d interactions. As the coating grows, decreases in inter-metallic bonding, coupled with increased intraceramic interac-tions, weaken the interfacial bonding. While a monolayer of ZrC is tightly bound to an Fe substrate (Wideal 3:05 J/m2), the adhesion decreases upon film thickening, with the asymptotic value of W idealad reached for 4 ML of ZrC (2.3 J/m2)