Structure and density of silicon carbide to 1.5 TPa and implications for extrasolar planets

Abstract

There has been considerable recent interest in the high-pressure behavior of silicon carbide, a potential major constituent of carbon-rich exoplanets. In this work, the atomic-level structure of SiC was determined through in situ X-ray diffraction under laser-driven ramp compression up to 1.5 TPa; stresses more than seven times greater than previous static and shock data. Here we show that the B1-type structure persists over this stress range and we have constrained its equation of state (EOS). Using this data we have determined the first experimentally based mass-radius curves for a hypothetical pure SiC planet. Interior structure models are constructed for planets consisting of a SiC-rich mantle and iron-rich core. Carbide planets are found to be ~10% less dense than corresponding terrestrial planets.

MXenes vs. clays: emerging and traditional 2D layered nanoarchitectonics

“…34 As for carbides, unlike the abundant clay silicates on Earth, only a few exoplanets appear to consist of a mantle dominated by carbides rather than silicates. 35 Carbides related to the MXene family derive from the “MAX” phases (hexagonal ternary two-dimensional materials, vide supra ), which in turn are usually synthesized by solid state reactions at high temperatures under an inert atmosphere, appearing as the most competitive method compared with alternative ways such as isostatic pressing, sputtering, or spark plasma sintering. 36 For example, the typical procedure for the synthesis of the Ti 3 AlC 2 typical MAX phase consists of the treatment of stoichiometric amounts of Ti, Al and C (as graphite), and grinding in ball mill equipment before reacting at 1400–1700 °C for 1–4 h in a tubular furnace under an Ar flux.…”

Uncertainty-aware molecular dynamics from Bayesian active learning for phase transformations and thermal transport in SiC

“…SiC is a wide-gap semiconductor with diverse applications ranging from efficient power electronics to nuclear physics and astronomy. With the discovery of a large number of extrasolar planets 22 , the compositions and processes under extreme conditions have led to a wide range of studies. In particular, SiC has been identified from the adsorption spectroscopy of carbon-rich extrasolar planets 23,24 , which has motivated numerous experimental and computational studies of its high temperature high pressure behavior.…”

A MHz X-ray diffraction set-up for dynamic compression experiments in the diamond anvil cell

“…Understanding kinetic effects is important to reconcile discrepancies between static and dynamic phase diagramsparticularly if material properties determined from dynamic compression studies are used to provide constraints on planetary interior models (Kraus et al, 2017;Wicks et al, 2018;Duffy & Smith, 2019;Coppari et al, 2021;Kim et al, 2022). However, despite the interest in rate-and timescale-related phenomena, material behaviour at intermediate compression rates ( _ " " = 10 À3 -10 3 s À1 ) remains relatively unexplored.…”