Theoretical insights into the crystal and fundamental properties of MgAl9Zn compound: First-Principles calculations

Abstract

Mg-Al-Zn series Alloys are a very significant class of magnesium alloys and play a vital role in future industrial and economic development due to its outstanding physical properties, such as excellent machinability, fine corrosion resistance, low cost-effectiveness, and so on. However, the structural phase transition mechanism and the evolution of electronic, mechanical and thermal properties under high pressure remain poorly known. Here, we have searched a series of crystal structures of MgAl9Zn alloy compound at pressure range from 0 GPa to 200 GPa by CALYPSO method. Our energetic and dynamic calculations suggest that the ground state structure of MgAl9Zn under ambient pressure is crystallized in the hexagonal phase with space group of P63 symmetry. As the pressure increased up to 54 GPa, a phase transition occurred, i.e., the P63 phase transforms to R3c phase. The electronic band structure results indicated that both P63 and R3c phases are metallic. The mechanical and thermal results show that, compared with P63 phase, the R3c phase possesses better strength and stronger abilities to absorb or release heats. The resent findings pave a way for future design of advanced alloyed materials.