Middle range ordering in chrysocolla and nano-crystalline spertiniite

Abstract

Structures of chrysocolla from Congo and synthesized Cu(OH)₂ nano-crystallite were analyzed by the anomalous X-ray scattering techniques. Environmental RDFs around Cu clarify Cu-O correlations corresponding to nearer four oxygen out of the distorted octahedral coordination. Although Cu-K edge EXAFS spectrum of chrysocolla is quite similar to that of nano-crystalline Cu(OH)₂, the Cu-Cu correlation around 3.3 Å observed in environmental-RDF showed different features. This result may indicate the unique structure of chrysocolla composed of local structural units of SiO₄ and Cu(O,OH)₆.