The first-principle studies of the crystal phase transitions: Fd3m-MgAl2O4→F4-3m-MgAl2O4

✍ Scribed by Liang Zhang; Guang-Fu Ji; Feng Zhao; Chuan-Min Meng; Dong-Qing Wei

• Publisher: Elsevier Science
• Year: 2011
• Tongue: English
• Weight: 322 KB
• Volume: 406
• Category: Article
• ISSN: 0921-4526
• DOI: 10.1016/j.physb.2010.10.054

✦ Synopsis

Magnesium aluminum spinel (MgAl 2 O 4 ) is a major constituent of the shallow upper mantle. It is of great geophysical importance to explore its physical properties under high pressure and temperature. The firstprinciple density functional theory (DFT) with the plane wave along with pseudopotential was employed to obtain the total energy for both Fd3m-MgAl 2 O 4 and F4-3m-MgAl 2 O 4 , which was used to generate the Gibbs free energy as a function of temperature and pressure with the quasi-harmonic Debye model. It is found that the phase transition temperature from Fd3m-MgAl 2 O 4 to F4-3m-MgAl 2 O 4 is beyond 452.6 K in the pressure regime studied, which is consistent with the experiment. The phase transition temperature is related to pressure by a linear function, i.e. T ¼8.05P +452.6, which is the first equation of this kind to describe the phase transition Fd3m-F4-3m. The elastic constants, equation of states and thermodynamic properties of Fd3m-MgAl 2 O 4 are also reported in this paper to make a complete study.