Neue Publikation zur Kristallchemie von Olivenit-Libethenit

A common feature in secondary arsenates in the substitution of the arsenate groups for phosphate. Such substitution is interesting from the practical point of view because it can lower the solubility of the resulting phase, thus increasing the retention of the toxic arsenic. In an effort to understand the arsenate-for-phosphate substitution, we investigate its crystal chemical features in a common substitution series olivenite-libethenite [Cu2(AsO4)(OH)-Cu2(PO4)(OH)]. We found that the solid solution is thermodynamically non-ideal, with small enthalpies of mixing. There is a clear discontinuity in the data, related to the monoclinic-orthorhombic phase transition within series, induced by chemical variations. Using spectroscopic techniques, we could determine that there is buildup of strain in the structure over short distances (5 A) but the strain is relieved over slightly longer distances (15 A). The data can be used to understand this and other similar solid solutions. For more details, see https://doi.org/10.5194/ejm-35-157-2023Externer Link.