Melting of CaSiO<sub>3</sub> Perovskite at High Pressure

Braithwaite, J. Spencer; Stixrude, Lars

doi:10.1029/2018gl081805

Cited by 18 publications

(34 citation statements)

References 39 publications

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“…Using our Z method and the same pseudopotentials, functional, energy cut‐off and cell‐size, our calculated T h is 8806 K at 105 GPa, which is roughly 1700 K higher than 7120 K at 103 GPa found by Braithwaite and Stixrude (2019). Calculations using a similar waiting time analysis as that of Braithwaite and Stixrude (2019) gave a T m of 6493 K at 105 GPa, about 1300 K higher than that reported by Braithwaite and Stixrude (2019) at the same density. To compare directly with the results reported in Figure 1, we also carried out Z‐method calculations using the PBE functional with similar input parameters for the electronic wave function as we used in the two‐phase calculations.…”

Section: Melting Curves Entropy and Kinetics Of Meltingmentioning

confidence: 70%

“…Cpv-curves: Two melting curves, based on classic pair potential molecular dynamics (MD) simulation by Liu et al (2010) include an upper curve, which is uncorrected for overheating, and a lower curve, corrected for 48% overheating by linking it to Zerr et al (1997). The melting curves of Braithwaite and Stixrude (2019) and Wilson and Stixrude (2021) are based on the Z method and two-phase thermodynamics (2PT) method, respectively. (b) The gray circular symbols represent melting points determined by multianvil experiments by Gasparik et al (1994).…”

Section: Figurementioning

confidence: 99%

“…The melting curve was therefore adjusted by a constant shift, T m = 0.48 × T c , in the entire pressure-range, to coincide with the melting temperature reported at 24 GPa by Zerr et al (1997). A similar approach was used in the DFT-MD study using the Z-method of Belonoshko et al (2006), where the melting curve was estimated from a series of MD runs in the micro-canonical (NVE) ensemble (Braithwaite & Stixrude, 2019). The simulated system is heated in steps to slightly above T h where the systems start to melt homogenously.…”

Section: Figurementioning

confidence: 99%

“…In addition, we explored two free energy methods, in which energies of the solid and liquid phases were calculated from separate one-phase simulation boxes to obtain the melting curve. We also used the Z-method to compare directly with the melting curve of Braithwaite and Stixrude (2019).…”

Section: Figurementioning

confidence: 99%

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Ab Initio Atomistic Simulations of Ca‐Perovskite Melting

Hernandez

Mohn

Guren

et al. 2022

Geophysical Research Letters

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The lower mantle is dominated by the two silicate perovskites, bridgmanite and Ca-perovskite, constituting about 77 and 5 mol%, respectively, of peridotites and about 34 and 24 mol%, respectively, of recycled oceanic crust of basaltic composition (e.g., Stixrude & Lithgow-Bertelloni, 2012). The melting curves of the end member components MgSiO 3 , CaSiO 3 and MgO in the system CaO-MgO-SiO 2 system (CMS) may inform about the crystallization history of the magma ocean and the nature of the ultra-low velocity zones (e.g., Trønnes et al., 2021). Although the melting curves for MgO-periclase and MgSiO 3 -bridgmanite are reasonably well established through the lower mantle pressure range, the Ca-perovskite melting curve remains poorly constrained, in particular at the lowermost mantle pressures (Figure 1). The melting of Ca-perovskite at 14-15 and 16-60 GPa, respectively, has been investigated by multi-anvil (Gasparik et al., 1994) and laser-heated diamond anvil cell (LH-DAC) experiments (Shen & Lazor, 1995;Zerr et al., 1997). Multi-anvil experiments with resistive heating and W-Re thermocouples might provide more accurate and reproducible melting temperatures than the LH-DAC experiments, which are in poor agreement with each other with a difference in melting temperature of about 880 K at 45 GPa. Nomura et al. (2017) performed multi-anvil experiments along the MgSiO 3 -CaSiO 3 join at 24 GPa and developed a thermodynamic model, anchored to the Zerr et al. (1997) melting curve. Although the experimentally based melting curves converge in the 2500-2800 K range at 14-16 GPa, the large variation in their dT/dp slopes yields increasing discrepancies with increasing pressure. The melting curve of Gasparik et al. (1994) is steeper (212 K/ GPa in the 13-15 GPa range) than those determined by the LH-DAC experiments of Shen and Lazor (1995) and Zerr et al. (1997). The latter slopes, measured in the 17-20 GPa range are 32 and 61 K/GPa, respectively. The Ca-perovskite melting curve has also been investigated by classical molecular dynamics (MD) based on empirical atomic potentials (Liu et al., 2010) and density functional theory (DFT) MD calculations (BraithwaiteAbstract Melting curves of Ca-perovskite (pure CaSiO 3 ) were determined by ab initio density functional theory, using two solid-liquid coexistence methods and two free energy approaches, in the form of thermodynamic integration and two-phase thermodynamics. The melting curves based on the solid-liquid coexistence methods and thermodynamic integration rise steeply from 2000 K at 14 GPa to 7000 K at 136 GPa. The melting temperature at 136 GPa is 1400 K higher than previous ab initio predictions. The high thermal stability of Ca-perovskite is linked to its high-symmetry isometric structure and consistent with experiments, demonstrating that Ca-perovskite is the most refractory phase in basaltic compositions in the lower mantle pressure range. The steep dT/dp slope of the melting curve also shows that the Ca-perovskite liquidus field expands relative to those of bridgmanite...

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Section: Melting Curves Entropy and Kinetics Of Meltingmentioning

confidence: 70%

Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

See 2 more Smart Citations

Ab Initio Atomistic Simulations of Ca‐Perovskite Melting

Hernandez

Mohn

Guren

et al. 2022

Geophysical Research Letters

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show abstract

“…The initial composition has an Mg number of 0.895, and it imitates the composition of pyrolite (McDonough & Sun, ; Lyubetskaya & Korenaga, ), with the ternary composition of MgO: 42.2 wt%, FeO: 8.7 wt%, and SiO 2 : 49.1 wt%. The existence of other oxides including Al 2 O 3 and CaO is likely to affect the melting temperature of mantle materials, although more studies are needed to better understand the melting of such oxides (Fiquet et al, ; Andrault et al, ; Braithwaite & Stixrude, ). Results of Monte Carlo inversion in our companion paper (Miyazaki & Korenaga, ) suggest that the nonideality of the mixing becomes negligible when the concentration of an oxide is low enough.…”

Section: Methodsmentioning

confidence: 99%

On the Timescale of Magma Ocean Solidification and Its Chemical Consequences: 2. Compositional Differentiation Under Crystal Accumulation and Matrix Compaction

Miyazaki

Korenaga

2019

JGR Solid Earth

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The solidification of a putative magma ocean sets the stage for subsequent subsolidus mantle convection. Whereas it may have resulted in a compositionally stratified mantle, the efficiency of relevant processes to cause chemical differentiation, such as crystal accumulation and matrix compaction, remains uncertain. The purpose of this study is to present the thermochemical structure of end-member cases where potential differentiation mechanisms are taking full effect. We employ a self-consistent thermodynamic model to make our model consistent in both thermal and chemical aspects. The accumulation of crystals at the base of magma ocean can enrich the upper mantle with iron, but such a global-scale compositional stratification is likely to be quickly eliminated by gravitational instability, leaving small-scale heterogeneities only. On the other hand, the compaction of solid matrix in the deep mantle creates a long-lasting molten layer above the core-mantle boundary. Our results suggest that the efficiency of compaction is the key factor to generate compositional stratification during solidification.

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Compositional effects in the liquid Fe–Ni–C system at high pressure

Posner

Steinle‐Neumann

2022

Phys Chem Minerals

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We performed molecular dynamics simulations based on density functional theory to systematically investigate the Fe–Ni–C system including (1) pure Fe and Ni; (2) binary Fe–Ni, Fe–C, and Ni–C; and (3) ternary Fe–Ni–C liquid compositions at 3000 K and three simulation volumes corresponding to pressure (P) up to 83 GPa. Liquid structural properties, including coordination numbers, are analyzed using partial radial distribution functions. Self-diffusion coefficients are determined based on the atomic trajectories and the asymptotic slope of the time-dependent mean-square displacement. The results indicate that the average interatomic distance between two Fe atoms (rFe–Fe) decreases with P and is sensitive to Ni (XNi) and C (XC) concentration, although the effects are opposite: rFe–Fe decreases with increasing XNi, but increases with increasing XC. Average rFe–C and rNi–C values also decrease with increasing XNi and generally remain constant between the two lowest P points, corresponding to a coordination change of carbon from ~ 6.8 to ~ 8.0, and then decrease with additional P once the coordination change is complete. Carbon clustering occurs in both binary (especially Ni–C) and ternary compositions with short-range rC-C values (~ 1.29 to ~ 1.57 Å), typical for rC-C in diamond and graphite. The self-diffusion results are generally consistent with high-P diffusion data extrapolated from experiments conducted at lower temperature (T). A subset of additional simulations was conducted at 1675 and 2350 K to estimate the effect of T on diffusion, yielding an activation enthalpy of ~ 53 kJ/mol and activation volume of ~ 0.5 cm3/mol.

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Melting of CaSiO₃ Perovskite at High Pressure

Cited by 18 publications

References 39 publications

Ab Initio Atomistic Simulations of Ca‐Perovskite Melting

Ab Initio Atomistic Simulations of Ca‐Perovskite Melting

On the Timescale of Magma Ocean Solidification and Its Chemical Consequences: 2. Compositional Differentiation Under Crystal Accumulation and Matrix Compaction

Compositional effects in the liquid Fe–Ni–C system at high pressure

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Melting of CaSiO3 Perovskite at High Pressure

Cited by 18 publications

References 39 publications

Ab Initio Atomistic Simulations of Ca‐Perovskite Melting

Ab Initio Atomistic Simulations of Ca‐Perovskite Melting

On the Timescale of Magma Ocean Solidification and Its Chemical Consequences: 2. Compositional Differentiation Under Crystal Accumulation and Matrix Compaction

Compositional effects in the liquid Fe–Ni–C system at high pressure

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Melting of CaSiO₃ Perovskite at High Pressure