Structures of di- and trioctahedral smectites intercalated with a Keggin like cation [Al13O4(OH)(24)(H2O)(12)](7+) have been studied using molecular mechanics simulations in the Cerius(2) modelling environment. The present study is focused on the effect of substitutions and distortions in the silicate layers on the crystal energy in these two types of intercalated layer structures. Detailed analysis of charge distribution has been carried out to explain the differences in behaviour of these two intercalated smectites. Tetrahedral substitution in the smectite layer reduces locally the negative charge of the smectite outside oxygen layer. This charge reduction favours the creation of preferential interlayer positions of the Keggin ion. The consequence of these preferential interlayer positions is a more homogeneous distribution of the intercalating ion.