New insight into the structural, mechanical, electronic, and thermodynamic properties of the monoclinic TMAl3-type aluminides

Although the monoclinic MoAl3 is a potential high-temperature alloy because of the high-temperature strength and good oxidation resistance, the structure and related properties of the monoclinic TMAl3 aluminides are entirely unclear. Here, we apply the first-principles calculation to study the structure, elastic, electronic, and thermodynamic properties of the monoclinic TMAl3. Five novel monoclinic TMAl3 aluminides: ScAl3, TiAl3, VAl3, CrAl3, and WAl3 are first predicted. The result shows that the hardness of the monoclinic TiAl3 is 13.0 GPa, which is larger than the tetragonal TiAl3. In particular, the calculated elastic modulus and hardness of WAl3 are larger than the other TMAl3 because of the heavy valence electronic density of metal W. Importantly, it is first found that the monoclinic MoAl3 shows the semiconductor properties with the band gap of 0.047 eV. In addition, the calculated Debye temperature of the monoclinic CrAl3 is 537.6 K, which is larger than the other monoclinic TMAl3. Essentially, the thermal stability of the monoclinic TMAl3 relies on the vibration of Al and Al-Al bond.

Automated summary

This study predicts and investigates the structure, elastic, electronic, and thermodynamic properties of five novel monoclinic TMAl3 aluminides using first-principles calculations, revealing that some of the alloys exhibit high hardness and stability.