Extensive ab initio calculations have been carried out to study the structure and bonding of hydrated UO2CO3 complexes using state-of-the-art techniques. The structures of aqueous UO2CO3 and its hydrated complexes have been further studied by considering the solvent as a polarizable continuum dielectric. The calculations have been carried out using polarization continuum, self-consistent isodensity polarizable continuum model, and conductor like screen models. The calculated uranyl frequencies of the hydrated UO2CO3 have been compared with the available vibrational frequencies and the nature of water binding has been analyzed using energy decomposition techniques. (C) 2003 Elsevier Science B.V. All rights reserved.