Periodic DFT calculation of the pressure-induced phase transition and thermodynamical properties of magnesium silicide polymorphs |
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Authors: | Ben-Hai YuFeng Peng Dong Chen Yong-Lei JiaMo-Lin Liu Bao-Ping Dong |
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Institution: | a College of Physics and Electronic Engineering, Xinyang Normal University, Changan Road, Xinyang City 464000, PR China b College of Physics and Electronic Information, Luoyang Normal University, Luoyang 471022, PR China |
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Abstract: | The plane-wave pseudo-potential method within the framework of first-principles is used to investigate the structural and elastic properties of Mg2Si in its low pressure phase (Fm-3m) and intermediate pressure phase (Pnma). The high-pressure lattice constants, the elastic constants, the elastic moduli and the anisotropy factors of the anti-cotunnite Mg2Si are presented and discussed. The results show that our system is mechanically stable. The reversible phase transition from anti-fluorite to anti-cotunnite structure is successfully reproduced through the quasi-harmonic Debye model. The phase boundary can be described as P=4.06826−6.95×10−3T+5.08838×10−5T2−4.24073×10−8T3. To complete the fundamental characteristics of these compounds we have analysed the thermodynamic properties such as thermal expansion, bulk modulus, isochoric heat capacity and Debye temperature in a pressure range 0-21 GPa and a temperature range 0-1200 K. The obtained results tend to support the experimental data when available. Therefore, the present results indicate that the combination of first-principles and quasi-harmonic approximations is an efficient scheme to simulate the high-temperature behaviours of semiconductors like Mg2Si. |
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Keywords: | Semiconductors Thermodynamic properties Phase transformation High-pressure |
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