Oxygen-molybdate distances

The three transition-metal molybdate layers defining the unit cell are stacked at a separation of c/3, analogous to the rhombohedral LDH precursor. In these layers, the position of the ordered vacancy capped by the molybdate groups follows the sequence A-B-C-A (where A, B, and C are the three threefold axes at x,y = 0,0 2/3,l/3 and l/3,2/3). This three layer arrangement is shown in Figure 5. Between each layer, in the space defined by the apical oxygens of six tetrahedral molybdates, lie ammonium ions. The positions of the nitrogen atoms follow the sequence C-A-B-C. The ammonium ions do not serve to connect the array of layers in the [00/] direction, the distance between the... 

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