Evaluation from first principles the structural stability of Mg containing different amounts of Al atoms under high pressure

摘要

The structural stability and phase transition of magnesium (Mg) containing different amounts of Al under high pressure was studied by means of first-principles total energy calculations. The cohesive energy calculations showed that the hcp and bcc structures of Mg-4.17 at%Al and Mg-8.33 at%Al were of the strong structural stability. The enthalpy for hcp and bcc structures of Mg was dependent upon the Al content. With increasing Al content from 0 to 8.33 at%, the enthalpy for hcp and bcc structures increased monotonously. Based on the enthalpy differences of the hcp and bcc structures under different pressures, the phase transition pressure under which the hcp→bcc structural phase transition may take place for pure Mg, Mg-4.17 at%Al and Mg-8.33 at%Al was 60 GPa, 70 GPa and 85 GPa, respectively, indicating that with the increasing Al content, the phase transition pressure became higher and the hcp→bcc transition was more difficult.