科研之友
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摘要
First-principles calculations are presented to resolve the possible pressure-dependent phases of Mg2Si. Although previous reports show that Mg2Si is characterized by the cubic antifluorite Fm (3) over barm structure at low pressures, the situation at higher pressures is less clear with many contradicting results. Here we utilize several methods to examine the stability, electron, phonon, and transport properties of this material as a function of pressure and temperature. We find that Mg2Si is thermodynamically stable at low and high pressures. Between 6 and 24 GPa, Mg2Si can transform into Mg9Si5, a defected compound, and vice versa, without energy cost. Perhaps this result is related to the aforementioned inconsistency in the structures reported for Mg2Si within this pressure range. Focusing solely on Mg2Si, we find a new monoclinic C2/m structure of Mg2Si, which is stable at high pressures within thermodynamical considerations. The calculated electrical conductivity and Seebeck coefficient taking into account results from the electronic structure calculations help us understand better how transport can be affected in this material by modulating pressure and temperature.
- 出版日期2016-3-22
