Structure and density of silicon carbide to 1.5 TPa and implications for extrasolar planets
Donghoon Kim, R. F. Smith, I. K. Ocampo, F. Coppari, M. C. Marshall, Mary Kate Ginnane, J. K. Wicks, S. J. Tracy, M. Millot, Amy Lazicki, J. R. Rygg, J. H. Eggert, T. S. Duffy
Abstract
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.