In this Letter, silicon nanocrystals doped with noble metal (Cu, Ag and Au) atoms have been studied by hybrid density functional theory. It is known that these metals play a significant role in Si nanowire growth, whereby Au is especially more favorable for this purpose. Our results show that the formation energies of noble metal impurities in Si nanocrystals are energetically high and hence less likely to be thermodynamically stable. In addition, our results show that Au atoms on the surfaces help promote the Si-Si covalent bonds in the nanostructures, whereas Cu and Ag induce some ionicity. (C) 2014 Elsevier B.V. All rights reserved.