The stability,optimized structure,binding energy,dipole moment and electronic gap of adamantane, C10H16,incorporating cage-centered small atoms and ions (X@cage, where X = Li0,+, Be2+, Na0,+, Mg2+, He, and Ne) have been studied at the B3LYP hybrid level of theory. A wide variety of atoms and ions can be encapsulated by adamantane. The complexes are more stable for smaller and more highly charged metallic guest species. The electronic HOMO– LUMO gaps of adamantane complexes are significantly affected by the inclusion of charged particles. The stability of the structures, the amount of the charges which are transferred between small particles and adamantane cage, and the change in the HOMO–LUMO gaps of adamantane complexes are nearly the same for the corresponding possible complexes. All these features mostly depend on the charge, the size and the type of the encapsulated particle. It is well recognized that the energy difference between highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) known as HOMO–LUMO gap (HLG) is a key parameter determining the conductance property. This parameter calculated for molecules and complexes .