As one of the simplest hydrocarbons, methane (CH4) has great potential in the research of superconductors. Based on the BCS theory, methane, colorless odorless gas that occurs abundantly in nature and as a product of certain human activities. Methane is the simplest member of the paraffin series of hydrocarbons, will be a potential high-temperature superconductor if it can transform into metal. However, pure CH4 is a wide-gap semiconductor at ambient pressure. Even if the pressure is set up to at least 520 GPa from experimental and theoretical studies, the band gap will not be close. This indicates that the conversion of pure CH4 to metal by simple pressurization presents a huge challenge. 

Dr. ZHONG Guohua and LI Wenjie at the Shenzhen Institutes of Advanced Technology (SIAT) of the Chinese Academy of Sciences have studied systematically structures and physical properties of methane doped by beryllium at low pressure and addressed these problems by the first-principles theory. 

The results show that based on the particle swarm optimization, density functional theory and density functional perturbation theory, CH4 can transform into metal and become a superconductor by doping Be. The researchers predicted the crystal structure, electronic and dynamical properties, and electron-phonon interaction of BeCH4 under certain pressure. Within the pressure range of 0-100 GPa, there are three thermodynamically stable phases in BeCH4, which are P-1 phase (0 ≤ P ≤ 25.6 GPa), a-P21 phase (25.6 ＜ P ＜ 50 GPa), and c-P1 phase (50 ≤ P ≤ 100 GPa). The P-1 phase can be realized the metallization under normal pressure, and a superconducting transition occurs, indicating that CH4 can be regarded as a new type of superconductor under electron doping and relatively low pressure. The metastable phase of a-P1 of BeCH4 has a superconducting critical temperature of 30 K at 80 GPa. Although the critical temperature of BeCH4 is less than room-temperature, this work provides a guiding road to the high temperature and low pressure superconductivity. 

The paper “Metallization and superconductivity in methane doped by beryllium at low pressure” was published on the International Journal of Modern Physics C, December 2019.