<i>Imma</i>phase of germanium at ∼80 GPa

Nelmes, R. J.; Liu, H.; Belmonte, S. A.; Loveday, J. S.; McMahon, M. I.; Allan, D. R.; Häusermann, Daniel M.; Hanfland, Michael

doi:10.1103/physrevb.53.r2907

Cited by 63 publications

(42 citation statements)

References 9 publications

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“…3,4 After its space group this intermediate phase was called Imma phase and corresponds to a body-centered orthorhombic Bravais lattice with two atoms in the unit cell (which will be called in the following BCO). Thus, the experimental structural sequence is found to be cd → β-tin → Imma → sh → .…”

Section: Introductionmentioning

confidence: 99%

Ab initiostudy of the β-tin→Imma→sh phase transitions in silicon and germanium

Gaál-Nagy

Pavone²,

Strauch³

2004

Phys. Rev. B

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We have investigated the structural sequence of the high-pressure phases of silicon and germanium. We have focussed on the cd → β-tin → Imma → sh phase transitions. We have used the plane-wave pseudopotential approach to the density-functional theory implemented within the Vienna ab-initio simulation package (VASP). We have determined the equilibrium properties of each structure and the values of the critical parameters including a hysteresis effect at the phase transitions. The order of the phase transitions has been obtained alternatively from the pressure dependence of the enthalpy and of the internal structure parameters. The commonly used tangent construction is shown to be very unreliable. Our calculations identify a first-order phase transition from the cd to the β-tin and from the Imma to the sh phase, and they indicate the possibility of a second-order phase-transition from the β-tin to the Imma phase. Finally, we have derived the enthalpy barriers between the phases.

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Section: Introductionmentioning

confidence: 99%

Ab initiostudy of the β-tin→Imma→sh phase transitions in silicon and germanium

Gaál-Nagy

Pavone²,

Strauch³

2004

Phys. Rev. B

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“…4), to an intermediate orthorhombic Imma phase at ∼75 GPa (ref. 5) and then to the simple hexagonal (sh) structure between 80 and 90 GPa (refs 6, 7, 8). At ∼100 GPa, Ge assumes a Cmca phase (an orthorhombic structure with 16 atoms per unit cell)7 and finally transforms to the hcp structure at 160–180 GPa (ref.…”

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confidence: 99%

Properties of the exotic metastable ST12 germanium allotrope

et al. 2017

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The optical and electronic properties of semiconducting materials are of great importance to a vast range of contemporary technologies. Diamond-cubic germanium is a well-known semiconductor, although other ‘exotic' forms may possess distinct properties. In particular, there is currently no consensus for the band gap and electronic structure of ST12-Ge (tP12, P43212) due to experimental limitations in sample preparation and varying theoretical predictions. Here we report clear experimental and theoretical evidence for the intrinsic properties of ST12-Ge, including the first optical measurements on bulk samples. Phase-pure bulk samples of ST12-Ge were synthesized, and the structure and purity were verified using powder X-ray diffraction, transmission electron microscopy, Raman and wavelength/energy dispersive X-ray spectroscopy. Optical measurements indicate that ST12-Ge is a semiconductor with an indirect band gap of 0.59 eV and a direct optical transition at 0.74 eV, which is in good agreement with electrical transport measurements and our first-principles calculations.

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“…ceeds not until 75 GPa [59]. Around 80 GPa, a hexagonal primitive arrangement forms and at 99 GPa, weak additional reflections indicate the onset of a structural transition into the orthorhombic Cmca structure isotypic to the corresponding silicon phase, so-called Si-VI, as well as Cs-V and Rb-VI [60,61].…”

Section: Silicon and Germanium (Tetrels)mentioning

confidence: 99%

Metallic high-pressure modifications of main group elements

Schwarz¹

2004

Zeitschrift Für Kristallographie - Crystalline Materials

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Abstract. The high-pressure structural chemistry of main group elements in the metallic state is reviewed under consideration of more recent determinations of atomic arrangements with to some extend unexpected complexity. Following the concept of the pressure-coordination rule, the number of nearest neighbours is employed as a guiding quantity to reveal systematic trends. Violations of the rule will be mainly discussed in the light of electronic ground state changes upon compression.

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Immaphase of germanium at ∼80 GPa

Cited by 63 publications

References 9 publications

Ab initiostudy of the β-tin→Imma→sh phase transitions in silicon and germanium

Ab initiostudy of the β-tin→Imma→sh phase transitions in silicon and germanium

Properties of the exotic metastable ST12 germanium allotrope

Metallic high-pressure modifications of main group elements

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