Pressure-induced superconductivity in the hydrogen-rich pseudobinary CaB−Hn compounds

Wen-Hua Yang; Wen-Cai Lu; Wei Qin; Hui-Juan Sun; Xu-Yan Xue; K. M. Ho; C. Z. Wang

doi:10.1103/PhysRevB.104.174106

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Pressure-induced superconductivity in the hydrogen-rich pseudobinary CaB−Hn compounds

Wen-Hua Yang, Wen-Cai Lu, Wei Qin, Hui-Juan Sun, Xu-Yan Xue, K. M. Ho, C. Z. Wang

DOI 10.1103/PhysRevB.104.174106 · Physical Review B

T1

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Abstract

The crystal structures of CaB−Hn compounds with n=1–12 in a pressure range of 50–300 GPa were studied using the genetic algorithm method and first-principles density-function theory calculations. Stable structures with stoichiometry of CaBH6 and CaBH7 were predicted in different pressure range. BH4, BH5, and BH6 units were found to be the main motifs in these compounds. Moreover, metastable Imm2 CaBH7 is dynamically stable above 180 GPa, with the formation of tetrahedral BH4 unit surrounded by Ca atom and H3 unit. Electron-phonon coupling (EPC) calculations reveal that the superconducting properties are closely related to the strong hydrogen-boron bonding of the BH4 unit in Imm2, and Tc can reach ∼200 K at 200 GPa. As the major units, BH4, BH5, and BH6 units exist in the Imm2, P2, and P21/m phases of CaBH7 at 300 GPa, respectively; the corresponding EPC parameter λ decreases with the increase of hydrogen content in CaBH7.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
CaBH6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	91	200 GPa	unknown
CaBH7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	190	200 GPa	unknown
CaBH8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	162	300 GPa	unknown
LaH10 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	250	170 GPa	unknown
LaH10 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	260	190 GPa	onset
LaBH8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	156	55 GPa	unknown
CaB2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	50	Pressure unresolved	unknown
CaB Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	6	20 GPa	unknown
B2H6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	125	360 GPa	unknown
CaH6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	235	150 GPa	unknown
CaBH6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	119	300 GPa	unknown
Ca2B2H13 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	89	300 GPa	unknown