Understanding γ-MnO2 by molecular modeling

De Wolff disorder, microtwinning, and point defects which are characteristic for gamma-MnO2 have been studied using molecular modeling. Particular attention was paid to the effects these defects have on the X-ray diffraction (XRD) pattern. Comparisons with observed XRD patterns allow identification of structural features in chemical (CMD) and electrochemical (EMD) manganese dioxide. The major factor determining the structure of gamma-MnO2 is de Wolff disorder. CMD materials are characterized by a larger percentage of pyrolusite while EMD materials contain more ramsdellite. Microtwinning occurs to a larger extent in EMD than in CMD materials. EMD materials are also higher in energy. (C) 2003 Elsevier Inc. All rights reserved.