Magnesium oxide at extreme temperatures and pressures studied with first-principles simulations

Soubiran, François; González‐Cataldo, Felipe; Driver, Kevin P.; Zhang, Shuai; Militzer, Burkhard

doi:10.1063/1.5126624

Cited by 20 publications

(26 citation statements)

References 83 publications

(138 reference statements)

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“…However, the behavior of this mineral at temperatures relevant to the conditions of shock experiments where ionization of the electronic shells take place, is unknown. sistent EOS across a wide range of density-temperature regimes relevant to WDM by combining results from state-of-the-art path integral Monte Carlo (PIMC) and DFT-MD simulation methods for first- [44] and second-row [45,46] elements.…”

Section: Introductionmentioning

confidence: 99%

Path integral Monte Carlo and density functional molecular dynamics simulations of warm dense MgSiO3

et al. 2020

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In order to provide a comprehensive theoretical description of MgSiO3 at extreme conditions, we combine results from path integral Monte Carlo (PIMC) and density functional molecular dynamics simulations (DFT-MD) and generate a consistent equation of state for this material. We consider a wide range of temperature and density conditions from 10 4 to 10 8 K and from 0.321 to 64.2 g cm −3 (0.1-to 20-fold the ambient density). We study how the L and K shell electrons are ionized with increasing temperature and pressure. We derive the shock Hugoniot curve and compare with experimental results. Our Hugoniot curve is in good agreement with the experiments, and we predict a broad compression maximum that is dominated by the K shell ionization of all three nuclei while the peak compression ratio of 4.70 is obtained when the Si and Mg nuclei are ionized. Finally we analyze the heat capacity and structural properties of the liquid.Recent ab initio simulations have shown that liquid silicates can exhibit very high conductivity at high pressure, which implies that super-Earths can generate magnetic fields in their mantle [43]. Therefore, it is desirable to have a first-principles EOS derived for much higher temperature and density conditions that span regimes of condensed matter, warm dense matter (WDM), and plasma physics in order to be used as a reference for shock experiments and hydrodynamic simulations. In recent works, a first-principles framework has been developed to compute con-arXiv:2001.00985v1 [cond-mat.mtrl-sci] 3 Jan 2020

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Section: Introductionmentioning

confidence: 99%

Path integral Monte Carlo and density functional molecular dynamics simulations of warm dense MgSiO3

et al. 2020

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“…The 1.08 factor equals the ratio of the density of defect-free diamond, 3.515 g cm −3 , and the initial density of the porous diamond in the experiment 3.25 g cm −3 . This scaling has been shown to work fairly well in shock compression experiments on porous materials [51][52][53][54][55][56]. If the shock Hugoniot curve for an initial density ρ A 0 is known but the curve for the initial density ρ B 0 is needed, one can approximately scale the densities of the original Hugoniot curve by the ratio of ρ B 0 /ρ A 0 .…”

Section: Ramp Compression Experiments Of Diamond and Equation Of Statementioning

confidence: 77%

Model of Ramp Compression of Diamond from Ab Initio Simulations

González-Cataldo,

Godwal,

Driver

et al. 2021

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Ramp compression experiments characterize high-pressure states of matter at temperatures well below those present in shock compression. However, because temperature is typically not directly measured during ramp compression, it is uncertain how much heating occurs under these shock-free conditions. Here, we performed a series of ab initio simulations on carbon in order to match the density-stress measurements of Smith et al. [Smith, et al., Nature 511, 330 (2014)]. We considered isotropically as well as uniaxially compressed solid carbon in the diamond and BC8 phases, with and without defects, as well as liquid carbon. Our idealized model ascribes heating during ramp compression to an initially uniaxially compressed cell transforming isochorically into an isotropically (hydrostatic equivalent) compressed state having lower internal energy, hence higher temperature so as to conserve energy. Multiple such heating events can occur during a single ramp experiment, leading to higher temperatures than with isentropic compression. Comparison with experiments shows that heating alone does not explain the equation of state measurements on diamond, instead implying that a significant uniaxial stress component remains present at high compression. The temperature predictions of our ramp compression model remain to be verified with future laboratory measurements.

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“…Rigorous discussions of the PIMC [15][16][17][18] and DFT-MD [19][20][21] methods have been provided in previous works, and the details of our simulations have been presented in some of our previous publications [22][23][24]. Here we summarize the methods and provide the simulation parameters specific to simulations of MgSiO 3 plasma.…”

Section: Methodsmentioning

confidence: 99%

Thermal and Pressure Ionization in Warm, Dense MgSiO$_3$ Studied with First-Principles Computer Simulations

González-Cataldo,

Militzer

2020

Preprint

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Using path integral Monte Carlo and density functional molecular dynamics (DFT-MD) simulations, we study the properties of MgSiO 3 enstatite in the regime of warm dense matter. We generate a consistent equation of state (EOS) that spans across a wide range of temperatures and densities (10 4 -10 7 K and 6.42-64.16 g cm −3 ). We derive the shock Hugoniot curve, that is in good agreement with the experiments. We identify the boundary between the regimes of thermal ionization and pressure ionization by locating where the internal energy at constant temperature attains a minimum as a function of density or pressure. At low density, the internal energy decreases with increasing density as the weight of free states changes. Thermal ionization dominates. Conversely, at high density, in the regime of pressure ionization, the internal energy increases with density. We determine the boundary between the two regimes and show that the compression maximum along the shock Hugoniot curve occurs because K shell electrons become thermally ionized rather than pressure ionized.

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Magnesium oxide at extreme temperatures and pressures studied with first-principles simulations

Cited by 20 publications

References 83 publications

Path integral Monte Carlo and density functional molecular dynamics simulations of warm dense MgSiO3

Path integral Monte Carlo and density functional molecular dynamics simulations of warm dense MgSiO3

Model of Ramp Compression of Diamond from Ab Initio Simulations

Thermal and Pressure Ionization in Warm, Dense MgSiO$_3$ Studied with First-Principles Computer Simulations

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