Ab initio two-phase molecular dynamics on the melting curve of SiO2

Usui, Yusuke; Tsuchiya, Taku

doi:10.1007/s12583-010-0126-9

Cited by 47 publications

(56 citation statements)

References 38 publications

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“…This is the only explanation consistent with the comparison between simulated [116] and experimental shock temperature [19,106,108,109] or sound speed data [105] for quartz and fused silica and the results of melting curve predictions [119,120] for SiO 2 from 20 to 160 GPa from MD simulations employing potentials sufficiently accurate to reproduce the boundaries between several solid phases.…”

Section: Supercooling Of Shock-melted Quartz and Fused Silicasupporting

confidence: 76%

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: Supercooling Of Shock-melted Quartz and Fused Silicasupporting

confidence: 76%

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

2018

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“…We applied kinetic energy cutoff of 50 Ry. The detailed conditions of the calculations were the same as those in our previous studies [e.g., Tsuchiya and Fujibuchi , ; Usui and Tsuchiya , ].…”

Section: Methodsmentioning

confidence: 99%

The P‐V‐T equation of state and thermodynamic properties of liquid iron

2014

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The equation of state (EoS) and thermodynamic properties of non-magnetic liquid iron were investigated from energy (E)-pressure (P)-volume (V)-temperature (T) relationships calculated by means of ab initio molecular dynamics simulations at 60-420 GPa and 4000-7000 K. Its internally consistent thermodynamic and elastic properties, in particular, density, adiabatic bulk modulus, and P wave velocity, were then analyzed. Compared to the seismological data of the Earth's outer core, pure liquid iron is found to have an 8-10% larger density and 3-10% larger bulk modulus than the Earth's values. Results also show that the P wave velocity of liquid iron has marginal temperature dependence as the bulk sound velocity of solid iron. The new EoS model and thermodynamic properties of liquid iron may serve as fundamental data for the thermochemical modeling of the Earth's core.

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“…Thermodynamic constraints of a steady shock in a continuum are applied to our MD simulations such that mass, energy and momentum are conserved everywhere in the shock wave. Conservation of momentum gives a relationship between stress and density called the Rayleigh line, and conservation of energy gives a relationship between energy and density called the Hugoniot condition 18 . Longer simulation times correspond to states further behind the shock front.…”

Section: Methodsmentioning

confidence: 99%

Nanosecond homogeneous nucleation and crystal growth in shock-compressed SiO2

Shen

Jester

et al. 2015

Nature Mater

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Understanding the kinetics of shock-compressed SiO2 is of great importance for mitigating optical damage for high-intensity lasers and for understanding meteoroid impacts. Experimental work has placed some thermodynamic bounds on the formation of high-pressure phases of this material, but the formation kinetics and underlying microscopic mechanisms are yet to be elucidated. Here, by employing multiscale molecular dynamics studies of shock-compressed fused silica and quartz, we find that silica transforms into a poor glass former that subsequently exhibits ultrafast crystallization within a few nanoseconds. We also find that, as a result of the formation of such an intermediate disordered phase, the transition between silica polymorphs obeys a homogeneous reconstructive nucleation and grain growth model. Moreover, we construct a quantitative model of nucleation and grain growth, and compare its predictions with stishovite grain sizes observed in laser-induced damage and meteoroid impact events.

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Ab initio two-phase molecular dynamics on the melting curve of SiO2

Cited by 47 publications

References 38 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

The P‐V‐T equation of state and thermodynamic properties of liquid iron

Nanosecond homogeneous nucleation and crystal growth in shock-compressed SiO2

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