High-resolution X-ray diffraction, DIFFaX, NMR and first principles study of disorder in the Li2MnO3–Li[Ni1/2Mn1/2]O2 solid solution

X-ray diffraction patterns of Li[Li(1 2x)/3NixMn2/3 x/3]O2 show reflections between 201 and 351, 2y (CuKa) due to Li2MnO3-like ordering of the transition metal (Ni, Mn and Li) layers. The ordering is rarely perfect, resulting in characteristic broadening and changes in the intensities of these reflections. Li MAS NMR studies of Li2MnO3 show that the [Li1/3Mn2/3] layers are well ordered, the disorder arising from the stacking of the layers in the c-direction. DIFFaX was used to model the Li2MnO3 XRD data and extract the stacking fault frequency. The results show that even well-ordered cation layers may show only weak or no superstructure reflections, if there is no or little ordering in the c-direction. r 2005 Elsevier Inc. All rights reserved.