Metastable phase transitions and structural transformations in solid-state materials at high pressure

McMillan, Paul F.; Shebanova, Olga; Daisenberger, Dominik; Quesada-Cabrera, Raúl; Bailey, E. Fiona; Hector, Andrew L.; Lees, Victoria; Machon, Denis; Sella, Andrea; Wilson, Mark

doi:10.1080/01411590701473010

Cited by 14 publications

(14 citation statements)

References 130 publications

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“…The improvement in agreement between the experimentally observed and DFT calculated Raman peak positions at V ind , compared to at V DAC , provides strong evidence for the presence of volume reduction due to unit cell distortion, as observed here using XRD and electron diffraction. Beyond the agreement with an indentation-induced bc8/r8 composite, the simulated shifts in peak position with varying volume/pressure are also consistent with observed shifts during decompression of expanded-volume clathrates [42] that the authors of Ref. [42] speculated are due to the formation of a bc8/r8 composite, a possibility to which our present results lend support.…”

supporting

confidence: 91%

“…Beyond the agreement with an indentation-induced bc8/r8 composite, the simulated shifts in peak position with varying volume/pressure are also consistent with observed shifts during decompression of expanded-volume clathrates [42] that the authors of Ref. [42] speculated are due to the formation of a bc8/r8 composite, a possibility to which our present results lend support.…”

supporting

confidence: 91%

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Formation of an r8-Dominant Si Material

et al. 2019

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The rhombohedral phase of Si (r8-Si), a promising semiconducting material, is formed by indentation together with the body-centered cubic phase (bc8-Si). Using a novel sample preparation method, X-ray diffraction is used to determine the relative volume of these phases in indented Si and allow observation of a distorted unit cell along the direction of indentation loading. Theoretical calculations together with these observations suggest the indent contains an intrinsic compression of ~4 GPa that stabilizes the R8 phase.

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confidence: 91%

supporting

confidence: 91%

Formation of an r8-Dominant Si Material

et al. 2019

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“…23,24 A recent study using Raman spectroscopy has found that the situation is more complex and that at least one intermediate metastable phase is formed during the compression and collapse of the clathrate structure. 25 Several studies have addressed the high-pressure behavior of clathrates with filled guest cages. Na 8 Si 46 apparently undergoes pressure-induced decomposition above P = 14 GPa, where characteristic peaks of the metallic hexagonal structure of Si begin to appear in the x-ray diffraction pattern.…”

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confidence: 99%

High-pressure phase transformations, pressure-induced amorphization, and polyamorphic transition of the clathrateRb6.15Si46

et al. 2009

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The type-I clathrate Rb 6.15 Si 46 with partly empty cage sites has been studied up to 36 GPa using Raman spectroscopy, synchrotron x-ray diffraction in diamond-anvil cells, and ab initio total-energy and latticedynamics calculations. A first phase transition is observed at 13Ϯ 1 GPa and a "volume collapse" transition within the clathrate structure is then observed at 24Ϯ 1 GPa. Pressure-induced amorphization into a highdensity amorphous ͑HDA͒ state occurs above P =33Ϯ 1 GPa. The HDA form transforms into a low-density amorphous polymorph during decompression. During the compression study using angle dispersive synchrotron x-ray diffraction techniques we measured bulk modulus parameters for rocksalt-structured TaO, included adventitiously in the clathrate sample ͓K 0 = 293͑3͒ GPa and K 0 Ј=5.4͑3͔͒.

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“…25 Although the activation barrier of the β→wII transformation is unknown, it is more likely to be high enough to exclude the room temperature transition. 2) The calculated Raman frequencies of wII-Si 3 N 4 could not match many strong peaks appeared in the measurements, 29,30 e.g., two observed peaks at about 500 cm −1 and 550 cm −1 at 38.2 GPa are absent for the wII phase. Meanwhile, β-Ge 3 N 4 , which is isostructural to β-Si 3 N 4 , is found to transform into the metastable polymorph δ-Ge 3 N 4 with hexagonal P 3 symmetry at room temperature.…”

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confidence: 99%

Equilibrium and metastable phase transitions in silicon nitride at high pressure: A first-principles and experimental study

Dong

McMillan

et al. 2011

Phys. Rev. B

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We have combined first-principles calculations and high pressure experiments to study pressure induced phase transitions in silicon nitride (Si3N4). Within the quasi-harmonic approximation, we predict that the α phase is always metastable relative to the β phase over the wide pressuretemperature range. Our lattice vibration calculations indicate that there are two significant and competing phonon-softening mechanisms in the β-Si3N4, while phonon softening in the α-Si3N4 is rather moderate.When the previously observed equilibrium high-pressure and high-temperature β→γ transition is by-passed at room temperatures (RT) due to kinetic reasons, the β phase is predicted to undergo a first-order structural transformation to a denser P6 phase above 39 GPa. The estimated enthalpy barrier height is less than 70 meV/atom, which suggests that the transition is kinetically possible around room temperatures. This predicted new high-pressure metastable phase should be classified as a "post-phenacite" phase. Our high-pressure X-ray diffraction experiment confirm this predicted room-temperature phase transition around 34 GPa. No similar RT phase transition is predicted for α-Si3N4. Furthermore, we discuss the differences in pressure dependencies of phonon modes in the α, β and γ phases and the consequences on their thermal properties. We attribute the phonon modes with negative Grüneisen ratios in the α and β phases as the cause of the predicted negative thermal expansion coefficients (TEC) at low temperatures in these two phases, and predict no negative TEC in the γ phase.

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Metastable phase transitions and structural transformations in solid-state materials at high pressure

Cited by 14 publications

References 130 publications

Formation of an r8-Dominant Si Material

Formation of an r8-Dominant Si Material

High-pressure phase transformations, pressure-induced amorphization, and polyamorphic transition of the clathrateRb6.15Si46

Equilibrium and metastable phase transitions in silicon nitride at high pressure: A first-principles and experimental study

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