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The crystal structures of boron hydrides in a pressure range of 50–400 GPa were studied using the genetic algorithm (GA) method combined with first-principles density functional theory calculations. BH4 and BH5 are predicted to be thermodynamically unstable. Two new BH2 structures with Cmcm and C2/c space group symmetries, respectively, were predicted, in which the B atoms tend to form two-dimensional sheets. The calculated band structures showed that in the pressure range of 50–150 GPa, the Cmcm-BH2 phase has very small gaps, while the C2/c-BH2 phase at 200–400 GPa is metallic. The superconductivity of the C2/c-BH2 structure was also investigated, and electron–phonon coupling calculations revealed that the estimated Tc values of C2/c-BH2 are about 28.18–37.31 K at 250 GPa. [ABSTRACT FROM AUTHOR]

The CO adsorption on the In-doped SnO 2 (1 1 0) surface has been studied by the first-principles calculations based on density functional theory. The study reveals that CO can be chemically adsorbed on the bridge site of the In-doped SnO 2 (1 1 0) surface transforming into CO 2 . The favorable oxidization of CO on the surface occurs with a small reaction barrier of 1.03 eV and is exothermic by 1.72 eV. These results suggest that the In-doping can contribute to the improvement of gas sensing properties of the SnO 2 -based sensors for CO gas. [ABSTRACT FROM AUTHOR]

Highlights: [•] The oxygen deficient h-WO3 (001) surfaces can be used to detect CO gas. [•] Oxygen vacancies exert negative effects on the sensitivity of the material. [•] The effect degree of oxygen vacancies is dependent on the defect density. [ABSTRACT FROM AUTHOR]

The crystal structures of boron hydrides in a pressure range of 50-400 GPa were studied using the genetic algorithm (GA) method combined with first-principles density functional theory calculations. BH4 and BH5 are predicted to be thermodynamically unstable. Two new BH2 structures with Cmcm and C2/c space group symmetries, respectively, were predicted, in which the B atoms tend to form two-dimensional sheets. The calculated band structures showed that in the pressure range of 50-150 GPa, the Cmcm-BH2 phase has very small gaps, while the C2/c-BH2 phase at 200-400 GPa is metallic. The superconductivity of the C2/c-BH2 structure was also investigated, and electron-phonon coupling calculations revealed that the estimated Tc values of C2/c-BH2 are about 28.18-37.31 K at 250 GPa.