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Ti2AlNb‐based alloy with a dominated orthorhombic phase is one of the most promising high‐temperature structural materials. In this work, the equilibrium volume, elastic, and thermodynamic properties of the ordered O phase with stoichiometric Ti2AlNb were predicted under different temperatures using first‐principles calculations based on density functional theory combined with quasi‐harmonic approximation (QHA). With the increase of temperature from 0 to 1300 K, the elastic properties decrease moderately and the bonding strength weakens slightly. The intrinsic properties of the Ti2AlNb O phase are ductile at all temperature considered. In order to explore the evolution mechanism of the temperature‐dependent elastic properties further, the density of state (DOS) has been analyzed. The stoichiometric Ti2AlNb O phase shows good high‐temperature mechanical and thermal stability, which is a kind of potential high‐temperature alloy applied in aeronautics industries.

Tc-based oxides are of interest because of their complex crystalline structures. In this work, the phonon dispersions, lattice distortions, and elastic constants of TcO at external pressures up to 120 GPa were comprehensively studied using first-principles calculations. It is found that the lattice dynamic stability of TcO can be assessed by fitting the Γ-Z acoustical phonon branch. The applied external pressure can be divided into three ranges: the low-pressure stable range, the middle-pressure buckling range, and the high-pressure unstable range. Interestingly, the variation tendency of the low-pressure stable range is very close to that of the high-pressure unstable range. On the other hand, the TcO lattice responds intensely to external pressure in the middle-pressure buckling range, which can be sustained under about 71 GPa pressure. More importantly, we have unraveled the pressure-induced lattice distortion in TcO, which leads to anomalous behaviors for the lattice constants, Tc-O bond lengths, and elastic constants at 10 and 20 GPa external pressures.