DOI 10.1007/s10820-006-9003-3 Journal of Computer-Aided Materials Design (2005) 12: 121–129 © Springer 2006 Theoretical study of benzene interaction on kaolinite ELTON A.S. CASTRO and JO ˜ AO B.L. MARTINS ∗ Laborat´ orio de Qu´ ımica Computacional, Instituto de Qu´ ımica, Universidade de Bras´ ılia, CP 4478, Bras´ ılia, CEP 70904-970, Brazil Received 12 January 2006; Accepted 13 February 2006; Published online 4 May 2006 Abstract. Clay minerals represent a growing research area in the development of new materials. Clay and clay-based materials have been widely investigated in efforts to design adsorbents. Further- more, adsorption has been applied in order to remove organics and as an important strategy to remediate soils and groundwater contaminated with petroleum hydrocarbons. Among clays, kaolinite, Al 2 Si 2 O 5 (OH) 4 , is a layered aluminosilicate of 1:1 clay minerals family. Therefore, we have performed semi-empirical AM1 and ab initio RHF/3-21G* calculations in order to investigate the benzene inter- action on kaolinite surface. The cluster model method was employed. Benzene structure was fully optimized. Molecular orbitals and electrostatic potential was also analyzed. The ab initio and semi- empirical results shows the benzene molecule largely tilted in relation to the hydroxyl layer. The π orbital of benzene has changed slightly indicating the interaction through the hydroxyl and benzene π orbital. Keywords: Ab initio, Aluminosilicates, Clay minerals 1. Introduction Aluminosilicates are important compounds present on the crust earth. They form a large number of minerals, which have a defined chemical structure. In particu- lar, zeolites and clays are valuable aluminosilicates for the industry. Clays and clay minerals have been widely used as drug delivery, water purification, water recy- cling, and remediation of soil contamination, and catalysts. Clay minerals represent a growing research area in the development of new materials as organic pollution in industrial waste streams is of environmental concern. Furthermore, adsorption has been applied to remove organic compounds. Therefore, clay-based materials have been widely investigated in efforts to design efficient and recyclable adsorbents as an important strategy to remediate soils and groundwater contaminated with petroleum hydrocarbons. Clay minerals have extremely small particle size, e.g, kaolinite of typically 2–10 μm. The tendency of these materials to exhibit substitutional and structural disorder restrains the development of more accurate description of bulk material properties. In particular, the small particle size often prevents using single-crystal diffraction tech- niques in order to determine the structural parameters. Thus, leading to ambiguities in the crystal structure [1, 2]. ∗ To whom correspondence should be addressed, E-mail: lopes@unb.br