A new high-pressure phase of strontium carbonate

Ono, Shigeaki; Shirasaka, Miki; Kikegawa, Takumi; Ohishi, Yasuo

doi:10.1007/s00269-004-0428-5

Cited by 33 publications

(23 citation statements)

References 31 publications

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“…1, relative to the enthalpy of the "post aragonite" phase. The transition from aragonite to "post aragonite" becomes energetically favorable at about 42 GPa, in agreement with previous DFT results 15,19,30,31 and experiment 14 . We performed calculations for the CaCO 3 -VI structure reported in Ref.…”

Section: Structure Searchessupporting

confidence: 81%

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Structures and stability of calcium and magnesium carbonates at mantle pressures

Pickard

Needs²

2015

Phys. Rev. B

137

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Ab initio random structure searching (AIRSS) and density functional theory methods are used to predict structures of calcium and magnesium carbonate (CaCO3 and MgCO3) at high pressures. We find a previously unknown CaCO3 structure which is more stable than the aragonite and "post aragonite" phases in the range 32-48 GPa. At pressures from 67 GPa to well over 100 GPa the most stable phase is a previously unknown CaCO3 structure of the pyroxene type with fourfold coordinated carbon atoms. We also predict a stable structure of MgCO3 in the range 85-101 GPa. Our results lead to a revision of the phase diagram of CaCO3 over more than half the pressure range encountered within the Earth's mantle, and smaller changes to the phase diagram of MgCO3. We predict CaCO3 to be more stable than MgCO3 in the Earth's mantle above 100 GPa, and that CO2 is not a thermodynamically stable compound under deep mantle conditions. Our results have significant implications for understanding the Earth's deep carbon cycle.

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Section: Structure Searchessupporting

confidence: 81%

“…At pressures of about 2 GPa calcite transforms to the aragonite structure 13 of P nma symmetry. At about 40 GPa aragonite transforms into the "post aragonite" (P mmn) structure of CaCO 3 , which is stable up to at least 86 GPa 14,15 . The low pressure magnesite phase of MgCO 3 has the same structure as calcite.…”

Section: Introductionmentioning

confidence: 99%

Structures and stability of calcium and magnesium carbonates at mantle pressures

Pickard

Needs²

2015

Phys. Rev. B

137

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“…However, unlike SiO 2 the V TD appears at higher pressures than the V CR and there is no quartz-like four-fold structure found in CO 2 . It is also unlike SiO 2 that at high temperatures all extended phases further transform into carbon dioxide carbonate (i-CO 2 ) [18] -a fully extended 2D ionic layer structure of the post aragonite of CaCO 3 (P2 1 2 1 2) [36]. Note that this P2 1 2 1 2 structure of i-CO 2 is in a sub/super-group relation with the P2 1 2 1 2 1 of V TD and P4 1 2 1 2 of α-cristobalite and is similar to the layer structure theoretically predicted earlier [8].…”

Section: Discussionmentioning

confidence: 99%

Transformation and structure of silicatelike CO2-V

et al. 2013

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We report the evidence of two different polymorphs for polymeric CO 2 -V in tridymite-like (V TD in P2 1 2 1 2 1 ) and β-cristobalite-like (V CR in I-42d) structures. The V TD phase is produced by laser-heating phase III (Cmca) above 40 GPa, whereas the V CR phase by laser-heating highly compressed phase II (P4 2 /mnm -iso-space group to stishovite) and IV (P4 1 2 1 2 -iso-space group to α-cristobalite) above 35 GPa. The density of the V CR (3.988 g/cm 3 ) is ~12 % larger than that of the V TD (3.559 g/cm 3 ) at 50 GPa, while the density difference reduces to ~4% at ambient pressure. This results in a substantially smaller bulk modulus (B o = 127 GPa, B'=5.6) for the V CR phase than that of the V TD (B o = 270 GPa, B'=1.9). The smaller density of the V TD is due to the open structure of corner shared CO4 tetrahedra and a great level of distortion in C-O-C angles resulting in a highly buckled layer structure; yet, the structural relationship gives rise to the specific transition to occur depending on the initial phase, either displacively from phase IV to phase V CR or diffusively from phase III to phase V TD . The results also provide new constraints for the phase/chemical transformation diagram of carbon dioxide.

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“…[19] Further study by Ono et al dismisses the trigonal structure in favor of an orthorhombic one with space group P 2 1 2 1 2. [20] Assignment of an orthorhombic post-aragonite phase was later supported by US-PEX structural simulations, which suggested the P mmn supergroup, and also predicted a further transformation into a post -post-aragonite C222 1 phase at megabar pressures. [21] Arapan et al performed density functional theory (DFT) calculations on CaCO 3 and found good agreement with the P mmn and C222 1 transition pressures predicted by Ref.…”

Section: Introductionmentioning

confidence: 87%

“…That the phase diagram of such a common and important mineral − and one exhibiting a wide array of stable structures which are relevant to geological processes in the Earth's mantle − has only begun to be unraveled experimentally since the turn of the century [18,20,24,27] is largely a result of experimental advances allowing powerful diagnostics such as X-ray diffraction to be performed in situ at combined high pressure and temperature. [30][31][32][33] A summary of the experimentallyconfirmed high-pressure phases of CaCO 3 is given in Table I alongside their onset pressures.…”

Section: −mentioning

confidence: 99%

Postaragonite phases of CaCO3 at lower mantle pressures

Smith

Lawler

Martínez-Canales

et al. 2018

Phys. Rev. Materials

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The stability, structure and properties of carbonate minerals at lower mantle conditions has significant impact on our understanding of the global carbon cycle and the composition of the interior of the Earth. In recent years, there has been significant interest in the behavior of carbonates at lower mantle conditions, specifically in their carbon hybridization, which has relevance for the storage of carbon within the deep mantle. Using high-pressure synchrotron X-ray diffraction in a diamond anvil cell coupled with direct laser heating of CaCO3 using a CO2 laser, we identify a crystalline phase of the material above 40 GPa − corresponding to a lower mantle depth of around 1,000 km − which has first been predicted by ab initio structure predictions. The observed sp 2 carbon hybridized species at 40 GPa is monoclinic with P 21/c symmetry and is stable up to 50 GPa, above which it transforms into a structure which cannot be indexed by existing known phases. A combination of ab initio random structure search (AIRSS) and quasi-harmonic approximation (QHA) calculations are used to re-explore the relative phase stabilities of the rich phase diagram of CaCO3. Nudged elastic band (NEB) calculations are used to investigate the reaction mechanisms between relevant crystal phases of CaCO3 and we postulate that the mineral is capable of undergoing sp 2 -sp 3 hybridization change purely in the P 21/c structure − forgoing the accepted post-aragonite P mmn structure.

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A new high-pressure phase of strontium carbonate

Cited by 33 publications

References 31 publications

Structures and stability of calcium and magnesium carbonates at mantle pressures

Structures and stability of calcium and magnesium carbonates at mantle pressures

Transformation and structure of silicatelike CO2-V

Postaragonite phases of CaCO3 at lower mantle pressures

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