Based on first-principles density-functional theory, we study the surface energetics and its electronic structure of fcc Fe(1 1 1) and hcp Fe(0 0 0 1), as well as the interfacial properties of the fcc Fe(1 1 1)/hcp Fe(0 0 0 1) system. Interestingly, we find the zero-temperature interfacial energy of this system to be negative, largely accounted for by chemical bonding at this interface. Consequently, this study provides an initial platform for the fundamental understanding of iron interfaces which is closely related to the stacking fault energy in iron alloys. (C) 2012 Elsevier B.V. All rights reserved.