High-pressure single-crystal structure determinations for ruby up to 90 kbar using an automatic diffractometer

d’Amour, H.; Schiferl, D.; Denner, Warren W.; Schulz, H.; Holzapfel, W. B.

doi:10.1063/1.325494

Cited by 204 publications

(48 citation statements)

References 38 publications

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“…Interestingly, these interatomic distances do not change over the whole Cr composition, in which the Cr-O1 (Cr-O2) distance is always larger than the Al-O1 (Al-O2) distance, indicating that the bonding in the Cr-O neighbors may be weaker than that in the Al-O neighbors. It is noted that the calculated values fairly agree with experimental values of 1.85 and 1.97Å for Al-O1 and Al-O2 in Al 2 O 3 [15], respectively, and 1.96 and 2.01Å for Cr-O1 and Cr-O2 in Cr 2 O 3 [16], respectively, as well as those in the dilute compound with x ¼0.002 [17].…”

Section: Resultssupporting

confidence: 79%

Structural stability and electronic properties in Al2O3–Cr2O3 mixed crystal

Kitaoka

Nakamura

Akiyama

et al. 2013

Journal of Crystal Growth

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Section: Resultssupporting

confidence: 79%

Structural stability and electronic properties in Al2O3–Cr2O3 mixed crystal

Kitaoka

Nakamura

Akiyama

et al. 2013

Journal of Crystal Growth

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“…1. Optimized values of a rho (lattice parameter), α rho (an angle between lattice vectors), and the internal parameters determining the position of aluminum and oxygen atoms inside the cell (Table 1) agree well with the results reported in [20] using the VASP code [16][17][18] and the experimental values [22]. The equilibrium lattice parameter differs insignificantly from the experimental value (0.8-1.2%) in both approaches within the GGA [23] and GGA-PBE [14] approximations.…”

Section: Bulk α-Al 2 Osupporting

confidence: 79%

Electronic structure of α-Al2O3 in the bulk and on the surface

2005

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“…13 and 19 -21. Let us first analyze results of calculations at 0 K. Parameters of the Vinet equation of state (22) for different phases of alumina are given in Table 1. One can notice good agreement with available experimental data at room temperature (23) and previous calculations (6). Fig.…”

supporting

confidence: 80%

The high-pressure phase of alumina and implications for Earth's D″ layer

Oganov

Ono

2005

Proc. Natl. Acad. Sci. U.S.A.

110

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Using ab initio simulations and high-pressure experiments in a diamond anvil cell, we show that alumina (Al2O3) adopts the CaIrO 3-type structure above 130 GPa. This finding substantially changes the picture of high-pressure behavior of alumina; in particular, we find that perovskite structure is never stable for Al 2O3 at zero Kelvin. The CaIrO3-type phase suggests a reinterpretation of previous shock-wave experiments and has important implications for the use of alumina as a window material in shock-wave experiments. In particular, the conditions of the stability of this phase correspond to those at which shock-wave experiments indicated an increase of the electrical conductivity. If this increase is caused by high ionic mobility in the CaIrO 3-type phase of Al 2O3, similar effect can be expected in the isostructural postperovskite phase of MgSiO 3 (which is the dominant mineral phase in the Earth's D؆ layer). The effect of the incorporation of Al on the perovskite͞postperovskite transition of MgSiO 3 is discussed.is an important ceramic material and a major chemical component of the Earth. High-pressure behavior of alumina is an issue of paramount importance for three reasons: (i) static compression experiments often rely on the ruby pressure scale (1), (ii) alumina is used as an optical window material in shock-wave experiments, and its properties (e.g., the electrical conductivity) will affect measurements, and (iii) alumina, although unlikely as an individual mineral phase in the Earth's mantle, is incorporated into mantle minerals and significantly affects their physical properties (e.g., refs. 2 and 3).According to theoretical (e.g., refs. 4 -6) and experimental (7-9) studies, at high pressures corundum transforms into the Rh 2 O 3 (II)-type structure. This well established transition, occurring at 80 -100 GPa (5-9), implies that the ruby pressure scale should not be used above Ϸ80 GPa in experiments that involve heating to temperatures where this phase transition will be kinetically feasible. Less clear evidence exists for a further transition. Lin et al. (9) reported that Rh 2 O 3 (II) structure is stable at least up to 130 GPa and 2,000 K, but above 130 GPa (at temperatures Ϸ1,500 K) shock-wave experiments of Weir et al. (10) indicated onset of an increase in the electrical conductivity that could be caused by a phase transition. Shock-wave Hugoniots of Al 2 O 3 compiled by Hama and Suito (11) also give evidence for a possible phase transition at 130 GPa with a small increase of density. Thomson et al. (6) predicted that an orthorhombic (Pbnm) perovskite structure becomes more stable than Rh 2 O 3 (II), but only above 200 GPa. The discovery of postperovskite CaIrO 3 -type polymorphs of Fe 2 O 3 (12) and MgSiO 3 (13,14) prompts the question of whether a similar phase exists for Al 2 O 3 .In our ab initio calculations, we consider four Al 2 O 3 polymorphs: corundum (space group R3 c), Rh 2 O 3 (II) (Pbcn), perovskite (Pbnm), and CaIrO 3 -type (Cmcm). Our calculations are based on the plane wave pseud...

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High-pressure single-crystal structure determinations for ruby up to 90 kbar using an automatic diffractometer

Cited by 204 publications

References 38 publications

Structural stability and electronic properties in Al2O3–Cr2O3 mixed crystal

Structural stability and electronic properties in Al2O3–Cr2O3 mixed crystal

Electronic structure of α-Al2O3 in the bulk and on the surface

The high-pressure phase of alumina and implications for Earth's D″ layer

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