The Crystal Structure of Lepidocrocite

摘要

The unit of structure, space group symmetry and detailed atomic arrangement of lepidocrocite are determined from xhyphen;ray data, and the existence and location of hydrogen bonds in the structure are established from considerations of interatomic distances. The orthorhombic lattice is end centered on (100), and has the axesa0= 3.87A,b012.51A, andc0= 3.06A. The space group isVh17mdash;Amam.The parameters are determined asuFe= mdash;0.332,uO= +0.282, anduOH= +0.075. The structure is described as consisting of ironhyphen;centered oxygen octahedra joined by the sharing of edges into twohyphen;dimensionally infinite layers, with the successive layers held together by hydrogen bonds. The relationship between the diasporehyphen;goethite structure and the bouml;hmitehyphen;lepidocrocite structure is discussed from the standpoint of the coordination theory, and found to depend on two alternative ways of satisfying the electrostatic valence rule.