First-principles study on the physical properties of TiB2 under high temperature and high pressure

Abstract:

This work reports the calculations of the physical properties of TiB2 under high temperature and high pressure using the first-principles method. The calculations include the structural parameter, elastic constants, bulk modulus, band structure, phonon dispersion, thermodynamic properties. These results are in agree well with other experimental and theoretical calculated values. By analyzing the E-V curves, the phonon dispersion curve, and the density of states (DOS), we prove that TiB2 is mechanically stable. From the results of B/G ratio and Poisson's ratio, the brittleness behavior of TiB2 is obtained. On the basis of the quasi-harmonic Debye model, we calculate the Debye temperature Θ and analyze the temperature and pressure dependences of the thermal expansion. The volumetric specific heat is very close to the Dulong-Petit limit at 1300 K. By analyzing the electron state density, it is found that TiB2 has metallic properties, the peak at Fermi level decreases, the pseudo gap widens, non-localization increases and covalent bond is enhanced as the pressure increases. All these results have proved that the crystal structure of TiB2 is stable.