Structural evolution and stabilities of (CuIn)nTe2 and ((CuIn)nTe2)− (n = 1–8) clusters via DFT study

Abstract

CuInTe₂ is a promising semiconductor with a tunable bandgap of 1.0-1.2 eV, enabling it to efficiently absorb sunlight and convert it into usable energy. Following this development, characterization of its structural and electronic properties is currently underway. In this study, the Vienna Ab Initio Simulation Package (VASP) with density functional theory (DFT) and plane-wave basis sets was used to investigate the structural and electronic properties of both neutral and anionic clusters. For (CuIn)_nTe₂ and ((CuIn)_nTe₂)⁻ (n = 1–8) clusters, geometric optimization revealed the lowest-energy isomers, all of which adopt cubic chalcopyrite structures. According to the results, the low-lying energy geometry of Cu₂In₂Te₂ and (CuInTe₂)⁻ clusters exhibit their maximum relative stability. The (CuIn)_nTe₂ thin-film experimental finding of 1.85 eV is a good match with their mean HOMO–LUMO gaps of 1.652 eV and 2.464 eV. Binding energy per atom increases with cluster size, although the HOMO–LUMO gap breaks at n = 5, most likely as a result of bond-specific interactions and orbital hybridization. The Cu₂In₂Te₂ cluster stands out with maximum HOMO–LUMO gap and dissociation energy, consistent with its enhanced stability. Adiabatic ionization potentials decrease with cluster size, indicating growing metallic character, while dissociation energies show odd–even oscillations but overall increase as size grows. Partial charge density analysis shows that both neutral and anion clusters are significant for semiconductor applications, including photovoltaic cells and related devices.