  Ab initio calculations of cadmium chalcogenide nanoclusters with terminating
groups (H, O, N, and C atoms bound to the surface sulfur) are considered as a
simulation for the species produced in typical synthesis of bio-conjugates with
luminescent quantum dots. The approaches based on the Hartree-Fock (HF) method
and density functional theory (DFT) are used assuming geometry optimization
keeping the tetrahedral symmetry. The geometry and electronic structure of CdX
(X=S, Se, Te) clusters with size up to Cd17 (HF) and Cd4 (DFT) bound with
hydrogen and -OH, -NH2, -CH3, and -CH2CH3 groups are calculated and the effects
of the terminating groups upon core clusters are discussed.
