Synthesis of Superconducting Cobalt Trihydride

Abstract

The Co-H system has been investigated through high-pressure high-temperature x-ray diffraction experiments combined with first principles calculations. On compression of elemental cobalt in a hydrogen medium, we observe fcc cobalt hydride (CoH) and cobalt dihydride (CoH 2 ) at 33 GPa. Laser heating CoH 2 in a hydrogen matrix at 75 GPa to temperatures in excess of ∼ 800 K, produces cobalt trihydride (CoH 3 ) which adopts a primitive structure. Density functional theory calculations support the stability of CoH 3 . This phase is predicted to be thermodynamically stable at pressures above 18 GPa and to be a superconductor below 23 K as critical temperature, T c . Theory

H2 Chemical Bond in a High-Pressure Crystalline Environment

“…Recent reports of superconductivity approaching room temperature − have galvanized attempts to synthesize hydrogen-rich materials. Much effort is being invested to understand their crystal structures and properties. − However, high-temperature hydride superconductivity is associated not with a particular crystal structure but with the stabilization of dense atomic hydrogen over molecular dimers. − In this paper, we address the fundamental issue of whether hydrogen in metal hydrides is atomic or molecular. − Hydrides provide a unique challenge for structural studies, especially under high pressure. From the experimental side, a major challenge is the very weak X-ray scattering by hydrogen atoms.…”

“…Neither compound has an identifiable Raman contribution from the stretching H 2 mode. Therefore, barium hydrides represent an ideal system to study how the change in stoichiometry alters the H 2 molecule within the solid. − Thus, a systematic investigation of the mechanisms involved in hydrogen intra-molecular bond weakening and the influence of the metallic atomic number is here undertaken as the route to understand the concepts of bond-weakening and chemical pre-compression.…”

“… 14 − 16 In this paper, we address the fundamental issue of whether hydrogen in metal hydrides is atomic or molecular. 17 − 19 Hydrides provide a unique challenge for structural studies, especially under high pressure. From the experimental side, a major challenge is the very weak X-ray scattering by hydrogen atoms.…”

Layer reconstruction, collapse and metallization of van der Waals bonded ZrS2 under high pressure

“…Phase transitions of TMDs can be induced by various external stimuli, such as mechanical exfoliation 8 , transverse electric eld 9 and intercalation 10 . Among these methods, applying pressure is a powerful and clean approach to modulate the electronic and crystal structures of TMDs without introducing impurities [11][12][13] . Taking the prototypal 2H phase (e.g.…”

Deviatoric stress-induced metallization, layer reconstruction and collapse of van der Waals bonded zirconium disulfide

“…Phase transitions of TMDs are induced by various external stimuli, such as mechanical exfoliation 9 , transverse electric field 10 and intercalation 11 . Among these methods, applying pressure is a powerful and clean approach to modulate the electronic and crystal structures of TMDs without introducing impurities [12][13][14] . Taking the prototypal 2H phase (e.g.…”