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Materials Data on BaI2 by Materials Project

BaI2 is Cotunnite structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 9-coordinate geometry to nine I1- atoms. There are a spread of Ba–I bond distances ranging from 3.52–4.18 Å. There are two inequivalent I1- sites. In the first I1- site, I1- is bonded to four equivalent Ba2+ atoms to form a mixture of edge and corner-sharing IBa4 tetrahedra. In the second I1- site, I1- is bonded in a 3-coordinate geometry to five equivalent Ba2+ atoms.

36 MATERIALS SCIENCE↗

Materials Data on BaI2 by Materials Project

BaI2 crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. there are two inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to nine I1- atoms. There are six shorter (3.55 Å) and three longer (3.79 Å) Ba–I bond lengths. In the second Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to nine I1- atoms. There are three shorter (3.50 Å) and six longer (3.85 Å) Ba–I bond lengths. There are two inequivalent I1- sites. In the first I1- site, I1- is bonded to five Ba2+ atoms to form distorted IBa5 trigonal bipyramids that share corners with six equivalent IBa4 tetrahedra, corners with ten equivalent IBa5 trigonal bipyramids, edges with six equivalent IBa4 tetrahedra, and edges with six equivalent IBa5 trigonal bipyramids. In the second I1- site, I1- is bonded to four Ba2+ atoms to form distorted IBa4 tetrahedra that share corners with ten equivalent IBa4 tetrahedra, corners with six equivalent IBa5 trigonal bipyramids, edges with two equivalent IBa4 tetrahedra, and edges with six equivalent IBa5 trigonal bipyramids.

36 MATERIALS SCIENCE↗

Madrid-2019 force field: An extension to divalent cations Sr2+ and Ba2+

In this work, we present a parameterization of Sr2+ and Ba2+ cations, which expands the alkali earth set of cations of the Madrid-2019 force field. We have tested the model against the experimental densities of eight different salts, namely, SrCl2, SrBr2, SrI2, Sr(NO3)2, BaCl2, BaBr2, BaI2, and Ba(NO3)2. The force field is able to reproduce the experimental densities of all these salts up to their solubility limit. Furthermore, we have computed the viscosities for two selected salts, finding that the experimental values are overestimated, but the predictions are still reasonable. Finally, the structural properties for all the salts have been calculated with this model and align remarkably well with experimental observations.

Chemistry↗

Wet chemical techniques for passivation of YBa2Cu3O7(7-x)

Wet chemical techniques are described for treatment of YBa2Cu3O(7-x) surfaces, resulting in the formation of native compounds with little or no reactivity to water. Promising native compounds include CuI, BaSO4, CuS, Cu2S, and the oxalates, all of which are either insoluble or have very low solubility in water. Treatment with dilute HI results in the formation of a native iodide film which is 80-90 percent CuI with small amounts of YI3 and BaI2. Treatment with dilute H2SO4 results in the formation of a film which is 95 percent BaSO4 and 5 percent Y2(SO4)3. Cu2S is formed on the surface with a dilute Na2S solution. An oxalate film with equal amounts of Y2(C2O4)3 and BaC2O4 results from treatment with dilute oxalic acid. X-ray photoelectron spectra show no significant changes when the sulfide, sulfate, or oxalate films are dipped in water, while the iodide film shows evidence of Cu(OH)2 formation.

Vasquez, R. P.↗