A novel crystalline SiCO compound

Abstract

Ab initio evolutionary structural searches have been performed on Si_xC_yO_2(x+y) compounds. A novel structure, with SiC₂O₆ stoichiometry and the P2₁/c space group is calculated to be stable against decomposition within a wide pressure window from 7.2 to 41 GPa, and metastable under ambient conditions. It consists of CO₃ units, linked to SiO₆ octahedra, supporting previous experimental studies. The evolution of the carbon environment towards tetrahedral CO₄ units, thus resembling the crystal chemistry of silicon, is predicted at higher pressures.