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

• Published in: Nature communications Vol. 13; no. 1; p. 2260
• Main Authors: Kim, D., Smith, R. F., Ocampo, I. K., Coppari, F., Marshall, M. C., Ginnane, M. K., Wicks, J. K., Tracy, S. J., Millot, M., Lazicki, A., Rygg, J. R., Eggert, J. H., Duffy, T. S.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 27.04.2022; Nature Publishing Group; Nature Portfolio
• Subjects: 704/2151/2809; 704/2151/330; 704/445/330; 704/445/862; Atomic structure; Carbon; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Compression; Equations of state; Extrasolar planets; Humanities and Social Sciences; Iron constituents; multidisciplinary; Planetary interiors; Science; Science (multidisciplinary); Silicon; Silicon carbide; Terrestrial environments; Terrestrial planets; X-ray diffraction
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-022-29762-y

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. Using ramp compression, silicon carbide was compressed to pressures of 1.5 terapascals, more than seven times higher than previous work. The results show that large carbon-rich exoplanets would be ~10% less dense than corresponding rocky planets.