MgO phase diagram from first principles in a wide pressure-temperature range

Belonoshko, Anatoly B.; Arapan, Sergiu; Martoňák, Roman; Rosengren, Anders

doi:10.1103/physrevb.81.054110

Cited by 96 publications

(87 citation statements)

References 58 publications

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“…9), we therefore eliminate with confidence the curves of Zerr and Boehler [1], Aguado and Madden [11], Strachan et al [8], Belonoshko [14], and Yoshimoto [15] because our temperature at 248 GPa exceeds their curves by 1300 to 3300 K, much more than our uncertainty. Summary of our shock temperature data from MgO preheated to 1850 K, the reported melting data [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and conventional shock temperature data [25,26]. All unlabeled data are the same as those shown in Fig.…”

Section: B Superheating Requires Incongruent Shock Melting or Recrysmentioning

confidence: 82%

“…The predicted melting temperature for MgO at the Earth's core-mantle boundary pressure, ≈135 GPa, ranges from 6000 to 9000 K [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] (Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

“…McWilliams et al [22] had poor constraints on the mechanical state of their MgO samples at shock speeds below ≈17.3 km/s (i.e., pressures below ≈525 GPa) due to loss of VISAR reflectivity, high uncertainties on all pressures due to sparse calibration assuming a linear Hugoniot despite the [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and conventional shock temperature data [25,26]. Typical uncertainties of the predicted melt lines are 100-200 K. Thicker lines indicate several melting curves that are close enough to be grouped and shown together.…”

Section: Introductionmentioning

confidence: 99%

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Thermodynamically complete equation of state of MgO from true radiative shock temperature measurements on samples preheated to 1850 K

2018

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Plate impact experiments in the 100-250 GPa pressure range were done on a 100 single-crystal MgO preheated before compression to 1850 K. Hot Mo(driver)-MgO targets were impacted with Mo or Ta flyers launched by the Caltech two-stage light-gas gun up to 7.5 km/s. Radiative temperatures and shock velocities were measured with 3%-4% and 1%-2% uncertainty, respectively, by a six-channel pyrometer with 3-ns time resolution, over a 500-900-nm spectral range. MgO shock front reflectivity was determined in additional experiments at 220 and 248 GPa using ≈50/50 high-temperature sapphire beam splitters. Our measurements yield accurate experimental data on the mechanical, optical, and thermodynamic properties of B1 phase MgO from 102 GPa and 3900 K to 248 GPa and 9100 K, a region not sampled by previous studies. Reported Hugoniot data for MgO initially at ambient temperature, T = 298 K, and the results of our current Hugoniot measurements on samples preheated to 1850 K were analyzed using the most general methods of least-squares fitting to constrain the Grüneisen model. This equation of state (EOS) was then used to construct maximum likelihood linear Hugoniots of MgO with initial temperatures from 298 to 2400 K. A parametrization of all EOS values and best-fit coefficients was done over the entire range of relevant particle velocities. Total uncertainties of all the EOS parameters and correlation coefficients for these uncertainties are also given. The predictive capabilities of our updated Mie-Grüneisen EOS were confirmed by (1) the good agreement between our Grüneisen data and five semiempirical γ (V ) models derived from porous shock data only or from combined static and shock data sets, (2) the very good agreement between our 1-bar Grüneisen values and γ (T ) at ambient pressure recalculated from reported experimental data on the adiabatic bulk modulus K s (T ), and (3) the good agreement of the brightness temperatures, corrected for shock reflectivity, with the corresponding values calculated using the current EOS or predicted by other groups via first-principles molecular dynamics simulations. Our experiments showed no evidence of MgO melting up to 250 GPa and 9100 K. The highest shock temperatures exceed the extrapolated melting curve of Zerr and Boehler by >3300 K and the upper limit for the melting boundary predictions of Aguado and Madden by >2600 K and those of Strachan et al. by >2100 K. We show that the potential for superheating in our shock experiments is negligible and therefore out data put a lower limit on the melting curve of B1 phase MgO in P -T space close to the set of consistent independent predictions by Sun et al., Liu et al., and de Koker and Stixrude.

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Section: B Superheating Requires Incongruent Shock Melting or Recrysmentioning

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Thermodynamically complete equation of state of MgO from true radiative shock temperature measurements on samples preheated to 1850 K

2018

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“…Employing "Z-method," Belonoshko et al have also successfully calculated MP for magnesium oxide. 17 The simulation techniques are similar as Secs. II-III B 2.…”

Section: Nacl At Ambient Pressurementioning

confidence: 99%

“…The fast-heating method, or so-called "heat-untilit-melts" method, 15 has lower computational requirements but exhibits hysteresis and overheating issues near phase transition. The "Z-method," 16 although successfully applied to several systems, 17,18 is still under debate 17,19,20 on its rigorous theoretical ground and its heavy dependence on simulation size and length.…”

Section: Introductionmentioning

confidence: 99%

Solid-liquid coexistence in small systems: A statistical method to calculate melting temperatures

Hong

Walle²

2013

The Journal of Chemical Physics

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We propose an efficient and accurate scheme to calculate the melting point (MP) of materials. This method is based on the statistical analysis of small-size coexistence molecular dynamics simulations. It eliminates the risk of metastable superheated solid in the fast-heating method, while also significantly reducing the computer cost relative to the traditional large-scale coexistence method. Using empirical potentials, we validate the method and systematically study the finite-size effect on the calculated MPs. The method converges to the exact result in the limit of large system size. An accuracy within 100 K in MP is usually achieved when simulation contains more than 100 atoms. Density functional theory examples of tantalum, high-pressure sodium, and ionic material NaCl are shown to demonstrate the accuracy and flexibility of the method in its practical applications. The method serves as a promising approach for large-scale automated material screening in which the MP is a design criterion. © 2013 AIP Publishing LLC. [http://dx

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High‐pressure melting of MgO from (Mg,Fe)O solid solutions

Lee

2014

Geophysical Research Letters

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Magnesium oxide (MgO) is a significant component of planetary interiors, particularly Earth's mantle and other rocky planets within and beyond our solar system; thus its high-pressure, high-temperature behavior is important to understanding the thermochemical evolution of planets. Laser-heated diamond-anvil cell (DAC) experiments on (Mg,Fe)O ferropericlase up to~40 GPa show that previous DAC experiments on MgO melting are too low, while previous multi-anvil experiments yield melting temperatures too high. Instead, our quasi-static experimental results are consistent with recent ab initio predictions as well as dynamic shock measurements. Extrapolated to the core-mantle boundary (CMB) of the Earth, MgO is expected to melt at~8000 ± 500 K, much greater than expected geotherm temperatures.

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MgO phase diagram from first principles in a wide pressure-temperature range

Cited by 96 publications

References 58 publications

Thermodynamically complete equation of state of MgO from true radiative shock temperature measurements on samples preheated to 1850 K

Thermodynamically complete equation of state of MgO from true radiative shock temperature measurements on samples preheated to 1850 K

Solid-liquid coexistence in small systems: A statistical method to calculate melting temperatures

High‐pressure melting of MgO from (Mg,Fe)O solid solutions

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