No evidence of metallic methane at high pressure

Recently reported superconductivity in lithium under pressure has renewed the interest in hydrogen and hydrogen-rich systems in the long standing quest for room temperature superconductivity. As the required metallization of pure hydrogen cannot be achieved within current experimental capabilities, it has been suggested that the chemical precompression exerted by heavier atoms in compounds with a large hydrogen content should lower the required pressures to attain the metallic transition in these alloys. Following the trend of analyzing group IVa hydrides, we present an ab initio analysis of pressure-induced metallization of methane. According to our calculations, the metallization of methane is not predicted to occur below 520 GPa, which corresponds to a compression factor of 7.5.