Despite the fact that experiment has provided evidence that MAo consists of three- dimensional cage structures, it was decided that a preliminary investigation on the relative stability of sheet, caged and fused caged structures ought to be performed. These results would then allow us to test the consistency of our theoretical calculations with this belief. Figure 1 shows a selection of the sheet and fused caged structures First of all, it must be noted that during the geometry optimization of the fused caged structure the bonds corresponding to five coordinate and four coordinate O atoms broke giving a caged structure. This shows that such structures are unstable alternatives for MAO