Publication Date:
2018
Description:
〈p〉Hydrogen-rich hydrides attract great attention due to recent theoretical (〈cross-ref type="bib" refid="R1"〉〈i〉1〈/i〉〈/cross-ref〉) and then experimental discovery of record high-temperature superconductivity in H〈sub〉3〈/sub〉S [〈i〉T〈/i〉〈sub〉c〈/sub〉 = 203 K at 155 GPa (〈cross-ref type="bib" refid="R2"〉〈i〉2〈/i〉〈/cross-ref〉)]. Here we search for stable uranium hydrides at pressures up to 500 GPa using ab initio evolutionary crystal structure prediction. Chemistry of the U-H system turned out to be extremely rich, with 14 new compounds, including hydrogen-rich UH〈sub〉5〈/sub〉, UH〈sub〉6〈/sub〉, U〈sub〉2〈/sub〉H〈sub〉13〈/sub〉, UH〈sub〉7〈/sub〉, UH〈sub〉8〈/sub〉, U〈sub〉2〈/sub〉H〈sub〉17〈/sub〉, and UH〈sub〉9〈/sub〉. Their crystal structures are based on either common face-centered cubic or hexagonal close-packed uranium sublattice and unusual H〈sub〉8〈/sub〉 cubic clusters. Our high-pressure experiments at 1 to 103 GPa confirm the predicted UH〈sub〉7〈/sub〉, UH〈sub〉8〈/sub〉, and three different phases of UH〈sub〉5〈/sub〉, raising confidence about predictions of the other phases. Many of the newly predicted phases are expected to be high-temperature superconductors. The highest-〈i〉T〈/i〉〈sub〉c〈/sub〉 superconductor is UH〈sub〉7〈/sub〉, predicted to be thermodynamically stable at pressures above 22 GPa (with 〈i〉T〈/i〉〈sub〉c〈/sub〉 = 44 to 54 K), and this phase remains dynamically stable upon decompression to zero pressure (where it has 〈i〉T〈/i〉〈sub〉c〈/sub〉 = 57 to 66 K).〈/p〉
Electronic ISSN:
2375-2548
Topics:
Natural Sciences in General
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