Sound velocities and thermodynamical properties of hcp iron at high pressure and temperature

Bouchet, Johann; Bottin, François; Antonangeli, Daniele; Morard, Guillaume

doi:10.1088/1361-648x/ac792f

Cited by 10 publications

(1 citation statement)

References 86 publications

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“…The details of estimation of v s are given in Methods. There are discrepancies in v p ‒ ρ and v s ‒ ρ relations of hcp-iron among ab initio calculations 17 – 19 as discussed by Bouchert et al 19 . Our result is generally consistent with calculations by Vocadlo et al 17 and Martorell et al 18 .…”

Section: Resultsmentioning

confidence: 99%

Sound velocity of hexagonal close-packed iron to the Earth’s inner core pressure

et al. 2022

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Here we determine the compressional and shear wave velocities (vp and vs) of hexagonal close-packed iron, a candidate for the main constituent of the Earth’s inner core, to pressures above 300 gigapascals using a newly designed diamond anvil cell and inelastic X-ray scattering combined with X-ray diffraction. The present results reveal that the vp and vs of the Preliminary reference Earth model (PREM) inner core are 4(±2)% and 36(±17)% slower than those of the pure iron, respectively at the centre of the core. The density and sound velocity of the PREM inner core can be explained by addition of 3(±1) wt% silicon and 3(±2) wt% sulphur to iron‒5 wt% nickel alloy. Our suggested inner core composition is consistent with the existing outer core model with oxygen, as the growth of the inner core may have created a secular enrichment of the element in the outer core.

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Section: Resultsmentioning

confidence: 99%

Sound velocity of hexagonal close-packed iron to the Earth’s inner core pressure

et al. 2022

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Speed of sound for understanding metals in extreme environments

Rasmussen,

Wilthan

2024

Applied Physics Reviews

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Knowing material behavior is crucial for successful design, especially given the growing number of next-generation energy, defense, and manufacturing systems operating in extreme environments. Specific applications for materials in extreme environments include fusion energy, semiconductor manufacturing, metal additive manufacturing, and aerospace. With increased applications, awareness of foundational science for materials in extreme environments is imperative. The speed of sound provides insights into phase boundaries, like shock-induced melting. Thermodynamic integration of the speed of sound enables the deduction of other desirable properties that are difficult to measure accurately, like density, heat capacity, and expansivity. Metrology advancements enable the speed of sound to be measured at extreme conditions up to 15 000 K and 600 GPa. This comprehensive review presents state-of-the-art sound speed metrology while contextualizing it through a historical lens. Detailed discussions on new standards and metrology best practices, including uncertainty reporting, are included. Data availability for condensed matter speed of sound is presented, highlighting significant gaps in the literature. A theoretical section covers empirically based theoretical models like equations of state and CALPHAD models, the growing practice of using molecular dynamics and density functional theory simulations to fill gaps in measured data, and the use of artificial intelligence and machine learning prediction tools. Concluding, we review how a lack of measurement methods leads to gaps in data availability, which leads to data-driven theoretical models having higher uncertainty, thus limiting confidence in optimizing designs via numerical simulation for critical emerging technologies in extreme environments.

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Mechanical properties of hcp Fe at high pressures and temperatures from large-scale molecular dynamics simulations

Deluigi,

Bringa

2024

Journal of Applied Physics

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We study the elastic behavior of hexagonal close-packed (hcp) Fe at the high temperature and pressure conditions of the Earth Core, using an embedded-atom method interatomic potential adjusted to those conditions. We calculate diffusivity, elastic constants, density, bulk modulus, shear modulus, and sound velocities vs temperature. We obtain reasonable agreement with ab initio simulations and with other empirical potential simulations. Our densities and shear modulus are slightly higher than those in the preliminary reference earth model for the core. Phase stability is discussed in terms of the Born criteria and free energies, finding that hcp is mechanically stable and that the free energy difference between hcp and body-centered cubic (bcc) is very small compared to the thermal energy. We compare our simulated shear modulus G to several analytical models, obtaining excellent agreement with the Atom in Jelium model by Swift and co-workers. Assuming that the yield strength Y is equal to the shear modulus G, Y=G/30, we find reasonable agreement with a recent parametrization of the Steinberg–Guinan model. These results can lead to future large-scale, multi-million simulations of Fe under core conditions for samples with microstructure like grain boundaries and twins, which might be present under those conditions.

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Sound velocities and thermodynamical properties of hcp iron at high pressure and temperature

Cited by 10 publications

References 86 publications

Sound velocity of hexagonal close-packed iron to the Earth’s inner core pressure

Sound velocity of hexagonal close-packed iron to the Earth’s inner core pressure

Speed of sound for understanding metals in extreme environments

Mechanical properties of hcp Fe at high pressures and temperatures from large-scale molecular dynamics simulations

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