First principles calculations have been performed to investigate the ground state properties of monoperiodic single-walled carbon nanotubes (CNTs) containing nanochain of aligned Ni atoms inside. Using the PBE exchange-correlation functional (E-xc) within the framework of density functional theory (DFT) we predict the clusterization of Ni filaments in (n,0) CNTs for n >= 9 and for (n, n) CNTs for n >= 6. The variations in formation energies obtained for equilibrium defective nanostructures allow us to predict the most stable Ni@CNT compositions. Finally, the electronic charge redistribution has been calculated in order to explore intermolecular properties leading to stronger Ni-Ni bond formation. (C) 2013 Elsevier B.V. All rights reserved.