Partial core vaporization during Giant Impacts inferred from the entropy and the critical point of iron

Li, Zhi; Caracas, Razvan; Soubiran, François

doi:10.1016/j.epsl.2020.116463

Cited by 10 publications

(15 citation statements)

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“…The critical point lies between the liquid and gas spinodals in density, and between the last isotherm where the pressure still reveals local extremes, and the first isotherm where the pressure is monotonously decreasing the decreasing density. For MgO, this places the critical point at 0.45-0.6 g/cm 3 in the density range and between 6500 and 7000 K in the temperature range. The corresponding pressures are on the order of 0.1-0.2 GPa (b).…”

Section: A Pair Distribution Functionmentioning

confidence: 93%

“…Because of its relevance for both planetary sciences and materials science, MgO has been studied extensively, both experimentally and theoretically, over a wide range of pressures and temperatures. At ambient pressure, the melting point lies at 3125 K and 3.6 g/cm 3 , and the boiling point is at 3870 K. The first numerical predictions of the melting line [10,11] overestimated the temperatures, while the first experimental results [12] underestimated them. Modern molecular-dynamics simulations predicted the melting of the B1 phase to occur at 3100 K and 0 GPa and at 9400 K and 240 GPa [13].…”

Section: Introductionmentioning

confidence: 94%

“…This behavior is best described using the van der Waals gas-liquid equilibrium model, which employs third-order polynomials. We approximate this model with a standard cubic polynomial least-squares fit relating the pressure to the density in accordance with other studies [3,39] (see the supplemental material for more details [40]). The cubic function allows us to quickly find the local minimum and maximum of the polynomial, which yields, respectively, the liquid and the gas spinodal points.…”

Section: -2mentioning

confidence: 99%

“…In temperature, it lies between the last isotherm whose pressure shows a local minimum and a local maximum, and the first isotherm that shows a monotonous decrease of pressure. This procedure was applied with success on various other material in the same phase space [3,24,26,42].…”

Section: -2mentioning

confidence: 99%

“…Currently, the most widely accepted hypothesis for the formation of our Moon is one such giant impact: a Marssized impactor, called Theia, collided with the proto-Earth. This giant impact melted, vaporized, and rendered supercritical a significant portion if not all of the impactor and of the proto-Earth [1][2][3][4][5], creating a large accretion disk from which the Moon formed. Using constitutive equations of the materials involved in the impact, smoothed-particle hydrodynamics (SPH) simulations [6] can describe some of the complex aspects of these giant impacts, and predict the outcome of such planetary impacts as well as the formation of protolunar disks.…”

Section: Introductionmentioning

confidence: 99%

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The critical point and the supercritical regime of MgO

Bögels

Caracas

2022

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The position of the critical point determines the top of the liquid-vapor coexistence dome, and is a physical parameter of fundamental importance in the study of high-energy shocks, including those associated with large planetary impacts. For most major planetary materials, like oxides and silicates, the estimated position of the critical point is below 1 g/cm3 at temperatures above 5000 K. Here we compute the position of the critical point of one of the most ubiquitous materials: MgO. For this, we perform first-principles molecular dynamics simulations. We find the critical density to be in the 0.4 - 0.6 g/cm3 range and the critical temperature in the 6500 - 7000 K range. We investigate in detail the behavior of MgO in the subcritical and supercritical regimes and provide insight into the structure and chemical speciation. We see a change in Mg-O speciation towards lower degrees of coordination as the temperature is increased from 4000 K to 10000 K. This change in speciation is less pronounced at higher densities. We observe the liquid-gas separation in nucleating nano-bubbles at densities below the liquid spinodal. The majority of the chemical species forming the incipient gas-phase consist of isolated Mg and O atoms and some MgO and O2 molecules. We find that the ionization state of the atoms in the liquid phase is close to the nominal charge, but it almost vanishes close to the liquid-gas boundary and in the gas phase, which is consequently largely atomic.&#160;This research was supported by the European Research Council under EU Horizon 2020 research and innovation program (grant agreement 681818&#8211;IMPACT to RC). This research was performed by access to supercomputing facilities via eDARI stl2816 grants, PRACE RA4947 grant, Uninet2 NN9697K grant.

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Section: A Pair Distribution Functionmentioning

confidence: 93%