The structure of fully H-inserted gamma-manganese dioxide compounds

Four materials forming a structural series of gamma-manganese dioxides were identified by an increasing proportion of microtwinning (17-100%) and a nearly constant amount of de Wolff disorder (P-r similar or equal to 0.41) as determined from their XRD patterns, Chemical I-I-insertion was performed in a nonaqueous environment and the structure of the fully I-I-inserted compounds investigated by XRD, In contrast to the starting materials the I-I-inserted compounds had similar XRD patterns which could be indexed on the basis that I-I-insertion caused expansion predominantly in the b orthorhombic direction, The anisotropic expansion changed the angle of the 021 and 061 microtwinning planes and caused strain along them, The demicrotwinning which resulted was the reason for the similarity of the XRD patterns of the II-inserted compounds, The common endpoint of II-insertion into the structural series was delta-MnOOH, which is an unmicrotwinned intergrowth structure based on groutite and manganite type layers reflecting the original intergrowth of ramsdellite and pyrolusite type layers in the original host structures. (C) 1996 Academic Press, Inc.