Experimental and theoretical studies of palygorskite clays

We have studied the structure and properties of palygorskite clays. A struc ture analysis was performed using two different models to reproduce the mon oclinic and orthorhombic lattices, using the atomic positions and cell para meters of palygorskite structure suggested by several authors, we simulated structures using Molecular Dynamics and Quantum Mechanics. Modifications o n the structure and elemental atom changes were made to obtain more stable configurations. X-ray diffraction patterns and high resolution electron mic roscopy images from simulated structures were compared with experimental re sults. It could be observed that orthorhombic model shows a better fitting than monoclinic models. These results might help to understand many of the properties of archaeological pigments, such as, Maya Blue, in which palygor skite clay was the main component. (C) 1999 Kluwer Academic Publishers.