Structure analysis of intercalated smectites using molecular simulations

Structures of di- and trioctahedral smectites intercalated with a Keggin li ke cation [Al13O4(OH)(24)(H2O)(12)](7+) have been studied using molecular m echanics 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 interca lated layer structures. Detailed analysis of charge distribution has been carried out to explain th e 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 creati on of preferential interlayer positions of the Keggin ion. The consequence of these preferential interlayer positions is a more homogeneous distributi on of the intercalating ion. (C) 2000 Elsevier Science B.V. All rights rese rved.