First-principles calculations on Mg/TiB2 interfaces

Abstract

In order to explore the interfacial structure of Mg (0001)/TiB2 (0001) interface and understand the heterogeneous nucleation potential of α-Mg grains on TiB2 particles, the electronic structure, adhesion work, bonding properties and interface energy of Mg(0001)/TiB2(0001) interface were investigated by the first-principles calculations method based on density functional theory (DFT). The Mg (0001) slabs with five atomic layers and TiB2 (0001) slabs with 9 atomic layers were adopted for interfacial models. Mg (0001)/TiB2 (0001) models with different stacking positions (“OT” stacking sequence, “HCP” stacking sequence and “MT” stacking sequence) of different terminations (Ti- and B-) were investigated. Metallic/covalent mixed bonds and ion bonds were formed respectively when Mg atoms combined with Ti-terminated TiB2 surface and B-terminated TiB2 surface. The interface energy of Mg/TiB2 interface is much larger than that of α-Mg/Mg melt interface, indicating that TiB2 particles possess poor nucleation potency for α-Mg grains from thermodynamical considerations.