Narrow Results

Metallization of methane (CH₄) has always been an interesting issue. Here, we report a study on the structure, metallization and superconductivity in K-doped CH₄ under pressure, based on the particle swarm optimization, density functional theory, and density functional perturbation theory. Summarizing the thermodynamical and dynamical stabilities, the electronic band structures, and the electron–phonon interaction calculations, we predicted that K-doped CH₄ in $P{2}_1∕m$ space-group is a metal and a possible superconductor in the pressure range of $70-90$ GPa. The superconducting critical temperature is about 12.7 K at 80 GPa. It was found that the charge transfer from K to CH₄ drives the metallization and mainly contributes to the electron–phonon interaction. The result confirms that CH₄ can become a metal and superconductor under the electron doping and the relative low pressure.

To explore the high-temperature superconductor at low pressures, we have investigated the crystal structures, electronic properties, and possible superconductivity in the case of methane (CH₄) doped by lithium in the pressure range of $0-100$GPa, based on the first-principles calculations. The results show that Li-intercalated CH₄ (Li_x(CH₄)${}_{1-x}$) can realize metallization and superconductivity at low pressures, even 5GPa. We find that there is a charge transfer between Li and CH₄, but the metallization is driven by the change of crystal field induce by doping instead of charge transfer. The critical temperture is predicted from 3.8K at 5GPa for LiCH₄ to 12.1K at 100GPa for Li(CH₄)₄. The low-pressure superconductivity of Li_x(CH₄)${}_{1-x}$ can be further optimized by adjusting component and pressure.

The aerobic oxidative cleavage of styrene C=C double bonds catalyzed by simple manganese porphyrin is reported. Under the catalysis of chloro(tetraphenylporphinato)manganese, the oxidative cleavage of the carbon-carbon double bond of the styrene with air yields benzaldehyde. Our results show that the oxidative cleavage and the epoxidation of the styrene double bond are the competition reactions in the styrene-manganese porphyrin-air system. The reaction temperature decided the product distribution. Under the conditions of 0.4 MPa air and 30 ppm of chloro(tetraphenylporphinato)manganese, the styrene conversion was 20.0% and the selectivity of benzaldehyde and styrene oxide was 81.7% and 12.7% respectively when the reaction temperature was 110°C. Styrene conversion was 92.5% and the selectivity of benzaldehyde and styrene oxide was 48.1% and 41.2% respectively when the reaction temperature was 120°C.

We report a collection of lowest-energy structures of hydrocarbon molecules C_nH_m (n = 6-18, m = 0 - 2n + 2) within the wide hydrogen chemical potential range. The genetic algorithm combined with Brenner's empirical potential is applied for the search. The resultant low-energy structures are further examined by ab initio quantum chemical calculations. The lowest-energy molecules with several additional low-energy structures are classified to four groups according to their structural motifs and the phase diagram with respect to carbon atom number and hydrogen chemical potential is presented. The results provide useful information for identifying the hydrocarbon molecules in the interstellar medium as well as addressing the hydrocarbon-related nanofragment growth in experiments.