The most stable structure of undecagold, or Au-11, clusters was predicted from our DFT calculations to be planar [L. Xiao, L. Wang, Chem. Phys. Lett. 392 (2004) 452; L. Xiao, B. Tollberg, X. Hu, L. Wang, J. Chem. Phys. 124 (2005) 114309.]. The structures of ligand protected undecagold clusters were shown to be three-dimensional experimentally. In this work, we used DFT calculations to study the ligand effect on the structures of Au-11 clusters. Our results show that the most stable structure of Au-11 is in fact three-dimensional when SCH3 ligands are attached. This indicates that the structures of small gold clusters are altered substantially in the presence of ligands. (c) 2006 Elsevier B.V. All rights reserved.