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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ca(BH)12 by Materials Project

CaB12H12 crystallizes in the monoclinic C2/c space group. The structure is zero-dimensional and consists of twenty-four boranediylradical molecules and four Ca(BH)6 clusters. In each Ca(BH)6 cluster, Ca2+ is bonded in a 6-coordinate geometry to six H+0.83+ atoms. There are a spread of Ca–H bond distances ranging from 2.37–2.42 Å. There are three inequivalent B1- sites. In the first B1- site, B1- is bonded in a single-bond geometry to one H+0.83+ atom. The B–H bond length is 1.21 Å. In the second B1- site, B1- is bonded in a single-bond geometry to one H+0.83+ atom. The B–H bond length is 1.21 Å. In the third B1- site, B1- is bonded in a single-bond geometry to one H+0.83+ atom. The B–H bond length is 1.20 Å. There are three inequivalent H+0.83+ sites. In the first H+0.83+ site, H+0.83+ is bonded in a water-like geometry to one Ca2+ and one B1- atom. In the second H+0.83+ site, H+0.83+ is bonded in a distorted water-like geometry to one Ca2+ and one B1- atom. In the third H+0.83+ site, H+0.83+ is bonded in a distorted water-like geometry to one Ca2+ and one B1- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CaB12(H3O2)4 by Materials Project

CaB5H5O4(BH)7(O2)2 crystallizes in the orthorhombic P2_12_12_1 space group. The structure is zero-dimensional and consists of twenty-eight boranediylradical molecules, eight oxygen molecules, and four CaB5H5O4 clusters. In each CaB5H5O4 cluster, Ca2+ is bonded in a 6-coordinate geometry to four H+0.67+ and two O2- atoms. There are a spread of Ca–H bond distances ranging from 2.32–2.62 Å. There are one shorter (2.32 Å) and one longer (2.54 Å) Ca–O bond lengths. There are five inequivalent B+0.50+ sites. In the first B+0.50+ site, B+0.50+ is bonded in a single-bond geometry to one O2- atom. The B–O bond length is 1.48 Å. In the second B+0.50+ site, B+0.50+ is bonded in a single-bond geometry to one H+0.67+ atom. The B–H bond length is 1.22 Å. In the third B+0.50+ site, B+0.50+ is bonded in a single-bond geometry to one H+0.67+ atom. The B–H bond length is 1.21 Å. In the fourth B+0.50+ site, B+0.50+ is bonded in a single-bond geometry to one H+0.67+ atom. The B–H bond length is 1.21 Å. In the fifth B+0.50+ site, B+0.50+ is bonded in a single-bond geometry to one H+0.67+ atom. The B–H bond length is 1.21 Å. There are five inequivalent H+0.67+ sites. In the first H+0.67+ site, H+0.67+ is bonded in a distorted L-shaped geometry to one Ca2+ and one B+0.50+ atom. In the second H+0.67+ site, H+0.67+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the third H+0.67+ site, H+0.67+ is bonded in a distorted bent 120 degrees geometry to one Ca2+ and one B+0.50+ atom. In the fourth H+0.67+ site, H+0.67+ is bonded in a distorted single-bond geometry to one Ca2+ and one B+0.50+ atom. In the fifth H+0.67+ site, H+0.67+ is bonded in a distorted water-like geometry to one Ca2+ and one B+0.50+ atom. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ca2+ and one O2- atom. The O–O bond length is 1.34 Å. In the second O2- site, O2- is bonded in a single-bond geometry to one O2- atom. The O–O bond length is 1.29 Å. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to two O2- atoms. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to one Ca2+, one B+0.50+, and one H+0.67+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Pressure-induced superconductivity in the hydrogen-rich pseudobinary CaB - H n compounds

Here, 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 CaB H 6 and CaB H 7 were predicted in different pressure range. BH 4 , BH 5 , and BH 6 units were found to be the main motifs in these compounds. Moreover, metastable Imm2 CaB H 7 is dynamically stable above 180 GPa, with the formation of tetrahedral BH 4 unit surrounded by Ca atom and H 3 unit. Electron-phonon coupling (EPC) calculations reveal that the superconducting properties are closely related to the strong hydrogen-boron bonding of the BH 4 unit in Imm2, and T c can reach ~200 K at 200 GPa. As the major units, BH 4 , BH 5 , and BH 6 units exist in the Imm2, P 2 , and P2 1 /m phases of CaB H 7 at 300 GPa, respectively; the corresponding EPC parameter λ decreases with the increase of hydrogen content in CaB H 7 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗