The hardness and electrical conduction in TiB2 and MgB2: Computational insights

Abstract

Achieving the coexistence of hardness and electrical conduction in materials is of great interest for fundamental scientific understanding and practical technological applications. Here, we investigated the hardness and electrical conduction of isostructural TiB2 and MgB2 based on the dislocation theory and first-principles calculations. The calculated hardness values obtained by the Sachs deformation texture model (20.20 GPa for TiB2 and 12.96 GPa for MgB2 at 300 K) are in good agreement with the measured ones (21.2 ± 1.1 GPa for TiB2 and 12.65 ± 1.39 GPa for MgB2). The analysis of hardness indicates that the dislocations on the {0001} and {10 1¯ 0} planes have the lower activation energy, and their movements are the main plastic deformation modes of TiB2 and MgB2. But, the hardness of TiB2 is larger than that of MgB2. From the perspective of the bonding mechanism, the strong Ti-B bonds associated with the hybridization of Ti 3d and B 2p states play a crucial role in the hardness of TiB2. Electrical conduction in TiB2 mainly results from the contribution of Ti 3d electrons, while it is from the partially occupied B σ- and π-bonding orbitals in MgB2.