The adsorption of 1,3-butanediol on ail oxygen-defect site of a CeO2(111) surface was investigated with density functional theory (DFT) and paired interacting orbital (PIO) calculations in connection with the investigation of a CeO2(111) stoichiornetric surface. At theoxygen-defect site, two adsorption structures were obtained by DFT Calculations. In the structures, the two oxygen atoms of the OH groups interact with exposed Cc cations at the oxygen-defect site. The adsorption structures at the oxygen-defect site are more stable than that on the stoichiometric surface. In the most stable adsorption structure, one hydrogen atom of the 2-position niethylene group interacts with the third Cc cation at the oxygen-defect site of the CeO2(111) surface. We confirmed the elongation of two C-O bonds and one C-H bond of the 2-position methylene group in the most stable adsorption Structure. We also executed PIO calculations of 1,3-butanediol-CeO2(111) systems to analyze interacting orbitals. In-phase interaction between the two oxygen atoms in 1,3-butanediol and Cc cations was observed, indicating that the 13-butanediol molecule is anchored by two O-Ce bonds. Out-of-phase interactions between O and C atoms at 1-position and between H and C atorns at 2-position were confirmed. (c) 2006 Elsevier Inc. All rights reserved.