We synthesized two C-S-H compounds from a mixture of carbon and sulfur in hydrogen-C : (H 2 S) 2 H 2 and from sulfur in mixed methane-hydrogen fluids-(CH 4 ) x (H 2 S) (2−x) H 2 at 4 GPa. X-ray synchrotron single-crystal diffraction and Raman spectroscopy have been applied to these samples up to 58 and 143 GPa, respectively. Both samples show a similar Al 2 Cu-type I4/mcm basic symmetry, while the hydrogen subsystem evolves with pressure via variously ordered molecular and extended modifications. The methane-bearing sample lowers symmetry to an orthorhombic Pnma structure after laser heating to 1400 K at 143 GPa. The results suggest that C-S-H compounds are structurally different from a common Im-3m H 3 S.

No abstract

The atomic and electronic structures of Cu 2 H and CuH have been investigated by high-pressure nuclear magnetic resonance spectroscopy up to 96 GPa, X-ray diffraction up to 160 GPa, and density functional theory-based calculations. Metallic Cu 2 H was synthesized at a pressure of 40 GPa, and semimetallic CuH at 90 GPa, found stable up to 160 GPa. For Cu 2 H, experiments and computations show an anomalous increase in the electronic density of state at the Fermi level for the hydrogen 1s states and the formation of a hydrogen network in the pressure range 43-58 GPa, together with high 1 H mobility of ∼10 −7 cm 2 /s. A comparison of these observations with results on FeH suggests that they could be common features in metal hydrides.