First-principles calculation on the structure stability, hydrogen trapping behaviour, and adhesion properties of the Zr(0001)-ZrC(100) interface

The structure stability, hydrogen trapping behaviour, and adhesion properties of the Zr(0001)-ZrC(100) interface are investigated by first-principle calculations. Periodically distributed distortion and stress-relaxed regions with lengths of 16.6 angstrom are formed to relax the lattice mismatch at the Zr(0001)-ZrC(100) interface. Homogeneous covalent 3Zr-C bonds are formed in the distortion region. The interfacial sinking effect exists only in the interface stress-relaxed region where the interstitial hydrogen has a considerably lower formation energy of -0.61 eV after the zero-point energy correction, than those in the interface distortion region, Zr, and ZrC bulk of 0.95, -0.10, and 1.30 eV, respectively. After the interstitial sites in the interface stress-relaxed region are fully occupied by hydrogen, the interface energy is significantly reduced from 2.34 to 1.52 J/m(2). The work of separation W-sep along the interface is approximately 3.78-3.91 J/m(2), while the brittle fracture of the Zr(0001)-ZrC(100) interface always occurs at the Zr matrix (along the Zr1 layer) with the lowest W-sep of 3.18-2.95 J/m(2). Hydrogen-induced electron localisation exists at the interface, which reduces the interface structure stability. In addition, a hydrogen passivation layer forms owing to the formation of Zr-H and C-H bonds at the interface.