Effects of Confinement on Structural Stability and Electronic Structure of Sodium Clusters

We have investigated structural stability and electronic properties of sodium clusters in the size range of 2-20 atoms as a function of confinement using real space density functional theory (DFT). We have selected lowest energy structures by examining lowest five isomers as a function of volume for six different compressions. The minimum volume considered is about 10% of the free box volume. We analyze energetics, eigenvalue spectra, molecular orbitals and charge density to examine the stability and electronic properties of the sodium clusters. Our calculations show the insignificant changes in the total energies until the volume gets reduced beyond the one third of the original volume. Once the critical volume is reached, the changes in the total energies are significant. This is accompained by the breaking of degeneracy of electronic levels, the increase in spacing between the energy states. The molecular orbital analysis shows the hybridization of sp-d orbitals, rotations, splitting, overlap of π-electrons and squeezing of molecular orbitals. It further shows the spill of electron density into the interstics region of clusters.