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A DFT Study on the Structural and Electronic properties of Cadmium Telluride (CdnTen) and Cadmium Zinc Telluride (Cd(n−m)ZnmTen) Clusters
Abstract
In this study, the structural and electronic properties of CdnTen and Cd(n−m)ZnmTen clusters have been studied using the plane wave based density functional theory (DFT). The QUANTUM ESPRESSO/PWSCF package employing the local density approximation (LDA) for the exchange correlation potential is used. In all calculations, the geometry optimization was employed in allowing the structures to fully relax. Structural properties viz. geometry, bond length and electronic properties like HOMO-LUMO gap, binding energy, second order energy difference and nature of bonding have been analyzed. As a result, we obtained that the binding energy increases with increasing cluster size and doping level. Zinc doped CdnTen clusters show greater binding energy than the undoped clusters. Planar structures are obtained for very small cluster sizes and in our simulation three dimensional structure is found at Cd4Te4 cluster in the lowest energy geometry. Clusters of certain sizes often have special properties, i.e. higher stability or larger HOMO-LUMO gap when compared with other clusters, such as Cd(3−m)ZnmTe3, m = 0, 1, 2 clusters. Thus, we can take it as a building block in the growth of the structures in our calculation. The partial charge density distribution of the HOMO and LUMO levels for CdnTen and Cd(n−m)ZnmTen clusters show that, the HOMO levels are predominantly localized on the Te atoms and the LUMO levels are distributed on both Cd and Zn atoms. Moreover, the LUMO levels are delocalized at the center of the clusters due to the hybridization of the molecular orbitals. The LDOS and energy level plots show discrete lines at the atomic level and the discreteness disappears as the cluster size increases.
Keywords: HOMO-LUMO, Pseudopotential, Cluster, Isomer.
