Temperature-dependence of structural and mechanical properties of TiB2: A first principle investigation

Abstract

High temperature mechanical and thermodynamic properties of TiB2 are important to its applications as ultrahigh temperature ceramic, which were not well understood. In this study, the thermodynamic and mechanical properties of TiB2 were investigated by the combination of first principle and phonon dispersion calculations. The thermal expansion of TiB2 was anisotropic, αc/αa is nearly constant (1.46) from 300 K to 1500 K, theoretically. The origination of this anisotropy is the anisotropic compressibility. The heat capacity at constant pressure was estimated from the theoretical entropy and fitted the experimental result quite well when higher-order anharmonic effects were considered. Theoretical isentropic elastic constants and mechanical properties were calculated and their temperature dependence agreed with the existed experiments. From room temperature to 1500 K, the theoretical slope is −0.0211 GPa·K−1, −0.0155 GPa·K−1, and −0.0384 GPa·K−1 for B, G, and E, respectively. Our theoretical results highlight the suitability of this method in predicting temperature dependent properties of ultrahigh temperature ceramics and show ability in selecting and designing of novel ultrahigh temperature ceramics.