  Silicon carbide has excellent physical properties, such as high stability,
thermal conductivity, and mechanical strength. It has been widely used in
high-power devices, catalysis, material processing, and other fields and is of
great significance in basic discipline research. We used crystal structure
search and first principles calculation to predict four new silicon carbide
structures stabilized within 3TPa. Pnma (SiC) replaces B1 (SiC) above 2.6TPa,
and the new component Si3C2 becomes the most stable after 2.5TPa. P4/mbm phase
Si3C2 under high pressure has electrode characteristics. The silicon-carbide
structure is metallic in the study pressure range, and the electrons contribute
most of the thermal conductivity, which is of great significance for the
thermal evolution of silicon-carbide-like terrestrial planets. In addition, we
propose a new silicon carbide planetary model and calculate the sound velocity
of Si3C2 under TPa. Therefore, our research has deepened the understanding of
silicon-carbide terrestrial planets' internal structure and thermal evolution,
explored the complex silicon-carbide phase space, and enriched the
silicon-carbide phase diagram.
