A study of the phase transitions, electronic structures and optical properties of under high pressure

Yu, F. Richard; Sun, Jie; Yang, Wei; Ronggang, Tian; Ji, Guang-Fu

doi:10.1016/j.ssc.2009.12.031

Cited by 42 publications

(21 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…According to the clearest pathway, Mg 2 Si transforms from the cubic F m3m to the orthorhombic P nma (anti-cotunnite) structure 6 at pressure P 7 GPa, followed by a transition to the hexagonal P 6 3 /mmc (Ni 2 In-type) structure at P 20 GPa. [7][8][9] This pathway does not include some (unresolved) hexagonal structures experimentally observed by Cannon et al 10 and Peun et al 11 Mg 2 Si was also found 12 to transfrom from F m3m to an unknown monoclinic phase at P 11 GPa. This new structural phase, which has also not been resolved, was reported 12 to remain stable up to P 37 GPa.…”

Section: Introductionmentioning

confidence: 77%

“…1 showing that the thermodynamic stability for the known phases at finite pressures agrees well with the ones reported by experimental and previous theoretical works. [6][7][8][9] In particular, the pressure-driven transitions of Mg 2 Si are F m3m → P nma → P 6 3 /mmc with two critical points at 8 GPa and 20 GPa. These two transitions are consistent with the two out of the three transitions observed experimentally 13 (the third one was suggested 13 to be related to the mixture of F m3m and P nma).…”

Section: Thermodynamically Stable Structures a Mg-si Binariesmentioning

confidence: 99%

See 1 more Smart Citation

High-pressure phases ofMg2Sifrom first principles

Huan

Tuoc

et al. 2016

Phys. Rev. B

View full text Add to dashboard Cite

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 antiflurite F m3m structure at low pressures, the situation at higher P 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.

show abstract

Section: Introductionmentioning

confidence: 77%

Section: Thermodynamically Stable Structures a Mg-si Binariesmentioning

confidence: 99%

High-pressure phases ofMg2Sifrom first principles

Huan

Tuoc

et al. 2016

Phys. Rev. B

View full text Add to dashboard Cite

show abstract

“…Mg 2 Si is an n-type semiconductor with an indirect band gap of 0.66-0.78 eV while Mg 2 Ge is a semiconductor with a slightly smaller indirect band gap of 0.57-0.74 eV [5]. Despite the numerous studies dedicated to Mg 2 Si, some discrepancies between experimental and simulation results exist especially concerning the existence or not of several different high pressure phases [6][7][8][9] and the formation enthalpies of both the pure compound [10][11][12][13][14][15] and the intrinsic defects (vacancies, antisites) [14][15].…”

Section: Introductionmentioning

confidence: 99%

Lattice stability and formation energies of intrinsic defects in Mg₂Si and Mg₂Ge via first principles simulations

Jund

Viennois

Colinet

et al. 2012

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

We report an ab initio study of the semiconducting Mg(2)X (with X = Si, Ge) compounds and in particular we analyze the formation energies of the different point defects with the aim of understanding the intrinsic doping mechanisms. We find that the formation energy of Mg(2)Ge is 50% larger than that of Mg(2)Si, in agreement with the experimental tendency. From a study of the stability and the electronic properties of the most stable defects, taking into account the growth conditions, we show that the main cause of the n doping in these materials comes from interstitial magnesium defects. Conversely, since other defects acting like acceptors such as Mg vacancies or multivacancies are more stable in Mg(2)Ge than in Mg(2)Si, this explains why Mg(2)Ge can be of n or p type, in contrast to Mg(2)Si. The finding that the most stable defects are different in Mg(2)Si and Mg(2)Ge and depend on the growth conditions is important and must be taken into account in the search for the optimal doping to improve the thermoelectric properties of these materials.

show abstract

“…17 First-principles calculations suggested the antifluorite-to-anticotunnite and anticotunniteto-Ni 2 In transitions. 18,19 In this study, we investigated the phase behavior of Mg 2 Si at pressures ranging from 0 to 11.3 GPa and temperatures ranging from 300 to 1530 K via in situ XRD analysis using synchrotron radiation and elucidated its phase relationships. We selected this pressure−temperature (p−T) window because it includes the p−T conditions required for the quenching experiments, wherein the structural phase transitions from the antifluorite phase were reported.…”

Section: ■ Introductionmentioning

confidence: 99%

Phase Relationship of Mg₂Si at High Pressures and High Temperatures and Thermoelectric Properties of Mg₉Si₅

2021

View full text Add to dashboard Cite

Magnesium silicide (Mg 2 Si) is a promising ecofriendly thermoelectric material, which has been extensively studied in recent times. However, its phase behavior at high pressures and temperatures remains unclear. To this end, in this study, in situ Xray diffraction analysis was conducted at high pressures ranging from 0 to 11.3 GPa and high temperatures ranging from 296 to 1524 K, followed by quenching. The antifluorite-phase Mg 2 Si decomposed to Mg 9 Si 5 and Mg at pressures above 3 GPa and temperatures above 970 K. The antifluorite-phase Mg 2 Si underwent a structural phase transition to yield a high-pressure roomtemperature (HPRT) phase at pressures above 10.5 GPa and at room temperature. This HPRT phase also decomposed to Mg 9 Si 5 and Mg when heated at ∼11 GPa. When 5Mg 2 Si decomposed to Mg 9 Si 5 and Mg, the volume reduced by ∼6%. Mg 9 Si 5 synthesized at high pressures and high temperatures was quenchable under ambient conditions. Thermoelectric property measurements of Mg 9 Si 5 at temperatures ranging from 10 to 390 K revealed that it was a p-type semiconductor having a dimensionless thermoelectric figure of merit (ZT) of 3.4 × 10 −4 at 283 K.

show abstract

A study of the phase transitions, electronic structures and optical properties of under high pressure

Cited by 42 publications

References 34 publications

High-pressure phases ofMg2Sifrom first principles

High-pressure phases ofMg2Sifrom first principles

Lattice stability and formation energies of intrinsic defects in Mg₂Si and Mg₂Ge via first principles simulations

Phase Relationship of Mg₂Si at High Pressures and High Temperatures and Thermoelectric Properties of Mg₉Si₅

Contact Info

Product

Resources

About

A study of the phase transitions, electronic structures and optical properties of under high pressure

Cited by 42 publications

References 34 publications

High-pressure phases ofMg2Sifrom first principles

High-pressure phases ofMg2Sifrom first principles

Lattice stability and formation energies of intrinsic defects in Mg2Si and Mg2Ge via first principles simulations

Phase Relationship of Mg2Si at High Pressures and High Temperatures and Thermoelectric Properties of Mg9Si5

Contact Info

Product

Resources

About

Lattice stability and formation energies of intrinsic defects in Mg₂Si and Mg₂Ge via first principles simulations

Phase Relationship of Mg₂Si at High Pressures and High Temperatures and Thermoelectric Properties of Mg₉Si₅