Rare earth element polyhydrides have been predicted to exhibit high-Tc superconductivity at extreme compressions. Through a series of in-situ high-pressure high-temperature x-ray powder diffraction experiments combined with density functional theory (DFT) calculations, we report the emergence of polyhydride species in the praseodymium-hydrogen system. We initially observe the formation of PrH3, which continuously increases in hydrogen content on compression towards PrH4. Laser heating PrH4 in a hydrogen medium at pressures of 85 GPa leads to the synthesis of both PrH9 and PrH7. Both structures are characterized by hexagonal arrays of praseodymium atoms surrounded by hydrogen clathrate cages.
Through a series of high-pressure x-ray diffraction experiments combined with in situ laser heating, we explore the pressure-temperature phase diagram of germanium (Ge) at pressures up to 110 GPa and temperatures exceeding 3000 K. In the pressure range 64-90 GPa we observe orthorhombic Ge-IV transforming above 1500 K to a previously unobserved high-temperature phase, which we denote as Ge-VIII. This high-temperature phase is characterised by a tetragonal crystal structure, space group I4/mmm. Density functional theory simulations confirm Ge-IV becomes unstable at high-temperatures and that Ge-VIII is highly competitive and dynamically stable at these conditions. The existence of Ge-VIII has profound implications for the pressure-temperature phase diagram, with melting conditions increasing to much higher temperatures than previous extrapolations would imply.
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
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.