Structure and Freezing of MgSiO
            <sub>3</sub>
            Liquid in Earth's Lower Mantle

Stixrude, Lars; Karki, Bijaya B.

doi:10.1126/science.1116952

Cited by 267 publications

(320 citation statements)

References 38 publications

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“…The AIMD simulations were performed at temperatures of 2,000, 1,800, 1,600 and 1,400°C in the liquid state. Previously AIMD simulations have been carried out to study the atomic structures of a variety of liquid melts [60][61][62][63] .…”

Section: Methodsmentioning

confidence: 99%

Deviation from high-entropy configurations in the atomic distributions of a multi-principal-element alloy

et al. 2015

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The alloy-design strategy of combining multiple elements in near-equimolar ratios has shown great potential for producing exceptional engineering materials, often known as 'high-entropy alloys'. Understanding the elemental distribution, and, thus, the evolution of the configurational entropy during solidification, is undertaken in the present study using the Al 1.3 CoCrCuFeNi model alloy. Here we show that, even when the material undergoes elemental segregation, precipitation, chemical ordering and spinodal decomposition, a significant amount of disorder remains, due to the distributions of multiple elements in the major phases. The results suggest that the high-entropy alloy-design strategy may be applied to a wide range of complex materials, and should not be limited to the goal of creating single-phase solid solutions.

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Section: Methodsmentioning

confidence: 99%

Deviation from high-entropy configurations in the atomic distributions of a multi-principal-element alloy

et al. 2015

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“…We chose the value of f = 0. [50] Spaulding et al [53] pressure (Mbar) pressure (Mbar) [39,51], the solidus [39,52], a proposed superliquidus liquid-liquid phase transition [53], and the ab initio melting curve of MgSiO 3 in the lower pressure perovskite phase [50], and (b) determinations of pure iron melting from experiment [54] and ab initio theory [55], brackets on the melting curve from ab initio theory [56] and the Lindemann law result based on subsolidus ab initio phonon calculations [57]. Arrows at the top indicate the pressure at the core-mantle boundary (a) and at the planetary centre (b).…”

Section: −2β Pmentioning

confidence: 99%

Melting in super-earths

Stixrude

2014

Phil. Trans. R. Soc. A.

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103

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We examine the possible extent of melting in rockiron super-earths, focusing on those in the habitable zone. We consider the energetics of accretion and core formation, the timescale of cooling and its dependence on viscosity and partial melting, thermal regulation via the temperature dependence of viscosity, and the melting curves of rock and iron components at the ultra-high pressures characteristic of superearths. We find that the efficiency of kinetic energy deposition during accretion increases with planetary mass; considering the likely role of giant impacts and core formation, we find that super-earths probably complete their accretionary phase in an entirely molten state. Considerations of thermal regulation lead us to propose model temperature profiles of super-earths that are controlled by silicate melting. We estimate melting curves of iron and rock components up to the extreme pressures characteristic of superearth interiors based on existing experimental and ab initio results and scaling laws. We construct superearth thermal models by solving the equations of mass conservation and hydrostatic equilibrium, together with equations of state of rock and iron components. We set the potential temperature at the core-mantle boundary and at the surface to the local silicate melting temperature. We find that ancient (∼4 Gyr) super-earths may be partially molten at the top and bottom of their mantles, and that mantle convection is sufficiently vigorous to sustain dynamo action over the whole range of super-earth masses.

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“…Subsequent experiments at higher pressures and high temperatures produced the equilibrium conditions [3][4][5][6][7][8][9][10] , and revealed a number of stable post-stishovite phases, including octahedrally coordinated silica with the CaCl 2 and a-PbO 2 structures and eventually to the pyrite structure [11][12][13][14][15][16][17] . The tetrahedron-to-octahedron transition in pure silica also exemplifies the universal phenomena in all silicate minerals throughout the mantle [18][19][20] .…”

mentioning

confidence: 99%

Polymorphic phase transition mechanism of compressed coesite

Shu

Cadien

et al. 2015

Nat Commun

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Silicon dioxide is one of the most abundant natural compounds. Polymorphs of SiO 2 and their phase transitions have long been a focus of great interest and intense theoretical and experimental pursuits. Here, compressing single-crystal coesite SiO 2 under hydrostatic pressures of 26-53 GPa at room temperature, we discover a new polymorphic phase transition mechanism of coesite to post-stishovite, by means of single-crystal synchrotron X-ray diffraction experiment and first-principles computational modelling. The transition features the formation of multiple previously unknown triclinic phases of SiO 2 on the transition pathway as structural intermediates. Coexistence of the low-symmetry phases results in extensive splitting of the original coesite X-ray diffraction peaks that appear as dramatic peak broadening and weakening, resembling an amorphous material. This work sheds light on the long-debated pressure-induced amorphization phenomenon of SiO 2 , but also provides new insights into the densification mechanism of tetrahedrally bonded structures common in nature.

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Structure and Freezing of MgSiO ₃ Liquid in Earth's Lower Mantle

Cited by 267 publications

References 38 publications

Deviation from high-entropy configurations in the atomic distributions of a multi-principal-element alloy

Deviation from high-entropy configurations in the atomic distributions of a multi-principal-element alloy

Melting in super-earths

Polymorphic phase transition mechanism of compressed coesite

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Structure and Freezing of MgSiO 3 Liquid in Earth's Lower Mantle

Cited by 267 publications

References 38 publications

Deviation from high-entropy configurations in the atomic distributions of a multi-principal-element alloy

Deviation from high-entropy configurations in the atomic distributions of a multi-principal-element alloy

Melting in super-earths

Polymorphic phase transition mechanism of compressed coesite

Contact Info

Product

Resources

About

Structure and Freezing of MgSiO ₃ Liquid in Earth's Lower Mantle