Pressure-induced structure, electronic, thermodynamic and mechanical properties of Ti2AlNb orthorhombic phase by first-principles calculations

Effects of pressure on lattice parameters, electronic, thermodynamic and mechanical properties of the fully ordered TiAlNb orthorhombic phase were studied using first-principles calculations based on density functional theory(DFT). The bonding nature for ordering orthorhombic TiAlNb was revealed quantitatively through the electronic structure analyzing. The external pressures play limited roles in the elastic anisotropy of the alloy due to the outstanding dynamical and mechanical stabilities under pressure. However, the shear modulus of O phase manifests anisotropic, where {010} shear planes are the easiest planes to cleave among the principal planes under all pressures.The heat capacities, volume expansions and thermal expansion coefficients were calculated using the quasi-harmonic approximation model based on the phonon dispersion curves. Meanwhile, the bulk modulus, Young’s modulus,shear modulus and the hardness are promptly enhanced under pressure. The predicted results give hints to design TiAlNb-based alloy as high-pressure applications.