First-principles study the mechanical, electronic, and thermodynamic properties of Mg-Al-Mn ternary compounds

Abstract

In recent years, magnesium alloys have been used more and more widely due to their excellent lightweight and good plasticity. But correspondingly, the requirements for the elastic modulus (E) are more demanding. Therefore, to improve the deficiency, we are committed to find a way to increase the E. In this work, the mechanical, electronic, and thermodynamic properties of the Mg-Al-Mn ternary compounds were explored effectively based on first-principles calculations. It was found that the stabilities of these six structures were verified by the phonon spectrum, cohesive energy, and density of state, which showed that Mg3(MnAl9)2 possessed the best stability. Furthermore, Mg3(MnAl9)2 also had the largest bulk modulus, shear modulus, and E with values of 78.39, 50.94, and 125.6 GPa, respectively, due to the high bond strength of Al-Al bonds, and this was also verified by Mulliken's population analysis. Not only that, the largest hardness was reflected in Mg3(MnAl9)2 with a value of 9.04 and 9.11 GPa in Chen's and Tian's models. Similarly, the thermodynamic results showed that Mg3(MnAl9)2 had the highest Debye temperature as a value of 540.29 K and the highest limiting thermal conductivity with values of 1.216 W m−1K−1 in Clarke's model and 0.945 W m−1K−1 in Cahill's model.