Germanium at high pressures

Menoni, Carmen S.; Hu, Jing; Spain, Ian L.

doi:10.1103/physrevb.34.362

Cited by 169 publications

(131 citation statements)

References 37 publications

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“…It has been observed in experiments that the onset of the cd→␤-Sn transition in Si and Ge occurs at lower pressures (ϳ8 GPa; cf. the values of p e and p t given in Table I for hydrostatic conditions) when the conditions in the pressure cell are nonhydrostatic (Baublitz and Ruoff, 1982a;Werner et al, 1982;Qadri et al, 1983;Hu et al, 1986;Menoni et al, 1986). The same effect is observed in binary compounds (see, for example, the case of GaAs in Besson et al, 1991).…”

Section: F Lessons About the Calculationssupporting

confidence: 55%

“…In Ge, slow decompression of the ␤-Sn phase leads to the tetragonal st12 phase, which persists metastably at zero pressure (Bundy and Kasper, 1963;Qadri et al, 1983;Menoni et al, 1986;Nelmes, McMahon, Wright, Allan, and Loveday, 1993). Rapid release of pressure leads, however, to the formation of a bc8 phase similar to that observed in Si, although in Ge it does not persist for long periods of time (Nelmes, McMahon, Wright, Allan, and Loveday, 1993).…”

Section: E Phases Obtained On Decrease Of Pressurementioning

confidence: 97%

“…Under pressures of about 10-11 GPa, the diamond phases of both Si and Ge undergo a transition to the metallic ␤-Sn phase (Jamieson, 1963a;Baublitz and Ruoff, 1982a;Werner et al, 1982;Qadri et al, 1983;Hu et al, 1986;Menoni et al, 1986). One of the earliest successes of firstprinciples pseudopotential theory was the determination by Yin andCohen (1980, 1982) that, from among the several candidates studied, the ␤-Sn structure was indeed favored in Si and Ge at high pressures, with a cd/ ␤-Sn coexistence pressure in quite good agreement with experiment.…”

Section: A Cd→␤-snmentioning

confidence: 99%

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High-pressure phases of group-IV, III–V, and II–VI compounds

et al. 2003

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Advances in the accuracy and efficiency of first-principles electronic structure calculations have allowed detailed studies of the energetics of materials under high pressures. At the same time, improvements in the resolution of powder x-ray diffraction experiments and more sophisticated methods of data analysis have revealed the existence of many new and unexpected high-pressure phases. The most complete set of theoretical and experimental data obtained to date is for the group-IVA elements and the group-IIIA-VA and IIB-VIA compounds. Here the authors review the currently known structures and high-pressure behavior of these materials and the theoretical work that has been done on them. The capabilities of modern first-principles methods are illustrated by a full comparison with the experimental data. CONTENTS

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Section: F Lessons About the Calculationssupporting

confidence: 55%

Section: E Phases Obtained On Decrease Of Pressurementioning

confidence: 97%

Section: A Cd→␤-snmentioning

confidence: 99%

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High-pressure phases of group-IV, III–V, and II–VI compounds

et al. 2003

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“…Changes in near edge region are observed above 11 GPa because of a structural transition from a cubic diamond phase to a tetragonal β-Sn phase [8][9][10] . The large energy decrease (∼ 1 eV) around 11 GPa in the pressure evolution of the absorption edge in Fig.2 (b), is consistent with the semiconductor to metal transition occurring simultaneously with the structural transformation [8][9][10] . The EXAFS signal χ(k), was obtained by subtracting the embedded-atom absorption background from the measured absorption coefficient and normalizing by the edge step.…”

Section: Experimental Results and Quantitative Data Analysismentioning

confidence: 99%

“…Crystalline Ge was chosen as a reference system since the structural transition observed at approximately 11 GPa has been widely investigated [8][9][10] . We demonstrate that the use of ND addresses the problem caused by diamond glitches.…”

Section: Introductionmentioning

confidence: 99%

High-pressure EXAFS measurements of crystalline Ge using nanocrystalline diamond anvils

et al. 2011

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High-pressure extended x-ray absorption fine structure (EXAFS) measurements on crystalline Ge demonstrate that the use of nano-crystalline diamond anvils can solve the glitch problem from single crystal diamond anvils and improve the quality of the data. Our results indicate that using nanocrystalline diamond anvils for high pressure EXAFS research can provide a large enough energy range for structural study up to four coordination shell distances. In particular, we obtained the pressure evolution of mean square relative displacement for the first neighbor shells of crystalline Ge and observed a different correlation effects for different coordination shells. The use of nanocrystalline diamond anvils will provide a breakthrough for high pressure EXAFS study, especially for amorphous compounds in which only limited structural information can be obtained by diffraction techniques.

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Raman microspectroscopy of nanocrystalline and amorphous phases in hardness indentations

Kailer¹,

Nickel²,

Gogotsi³

1999

J. Raman Spectrosc.

160

131

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During hardness indentation, materials are subjected to highly localized stresses. These stresses not only cause crack formation and plastic deformation by dislocation gliding, but a complete change of the crystal structure and formation of amorphous phases or high-pressure polymorphs can occur in the zone of maximum contact stresses. Such contact-induced phase transformations were observed in hard and brittle materials including semiconductors (Si, Ge, GaAs and InSb) and common ceramic materials such as SiC and SiO 2 (a-quartz and silica glass). A prime tool for their investigation is the Raman microspectroscopy of hardness indentations. In Si and Ge, there is an initial transformation to metallic high-pressure phases upon hardness indentation and a subsequent formation of crystalline, nanocrystalline, or amorphous phases depending on the conditions of the hardness test, in particular the unloading rate. A phase transformation occurs also in InSb, whereas the results for GaAs do not give sufficient evidence for phase transformations. Indentationinduced amorphization has been observed in SiC and quartz. Even diamond has been shown to undergo amorphization and phase transformation under nonhydrostatic stress conditions imposed by indentation tests.Plate 1. Light micrograph of (a) a Vickers impression in diamond, (b) typical Raman spectrum from the central part of the impression and Raman intensity images showing (c) distribution of diamond and (d) graphite. Colour change from dark blue to yellow indicates the increase of the Raman band intensity from zero to the maximum. (Excitation wavelength: 632.8nm)

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Germanium at high pressures

Cited by 169 publications

References 37 publications

High-pressure phases of group-IV, III–V, and II–VI compounds

High-pressure phases of group-IV, III–V, and II–VI compounds

High-pressure EXAFS measurements of crystalline Ge using nanocrystalline diamond anvils

Raman microspectroscopy of nanocrystalline and amorphous phases in hardness indentations

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