Atomic structures and energetics of heterophase interfaces among Fe(100), TiC(110) and Mo2C(001) surfaces: insights from first-principles calculations

Abstract

Atomic structures and interfacial energies of Fe(100)/TiC(110), Fe(100)/Mo₂C(001) and TiC(110)/Mo₂C(001) interfaces were studied by using first-principles calculations. Convergence testing of surface energy demonstrates that Fe(100) and TiC(110) slabs with more than five atomic layers, and Mo- and C-terminated Mo₂C(001) slabs with six and seven atomic layers, exhibit bulk-like properties inside the interface models. Slab supercells of five different heterophase interfaces composed of any two surfaces among Fe(100), TiC(110) and Mo₂C(001) with Mo- and C-terminations were constructed with low lattice mismatches below 6%, and their atomistic relaxations were carried out. Our calculations for interfacial work of adhesion, interface binding energy and interfacial energy demonstrate that the Fe/Mo₂C interface has stronger interfacial binding and higher thermodynamic stability than the Fe/TiC interface, while the TiC/Mo₂C interface exhibits stronger interfacial binding but lower stability than the Fe/TiC interface. The reason is that the interfacial Fe–C chemical bonds are weaker than the Mo–C and Ti–C bonds as revealed by analysis of electronic charge density difference. The present work can provide guidelines to improve the performance of Fe-based composites.