Impact of hetero-atom doping on electronic structure and reactivity of anionic Al13− cluster: a combined density functional theory and global optimization investigation

Abstract

Using density functional theory (DFT) in combination with particle swarm optimization (PSO) algorithm, we have investigated the role of group III and 4d/5d series of transition metal dopants on the structure and electronic properties of the icosahedral anionic Al₁₃⁻ cluster. Our results reveal that doping significantly modifies the structural characteristics of the Al₁₃⁻ cluster leading to geometries with the dopant occupying both endohedral and apical sites. This geometric transformation leads to notable alterations in the electronic properties, as evident from the computed binding energy per atom, HOMO–LUMO gap, vertical detachment energy, and vertical electron affinity. The findings indicate that doping enhances the stability of the anionic Al₁₃⁻ cluster. BAl₁₂⁻ cluster and 4d- and 5d-doped Al₁₃⁻ clusters generally depict enhanced binding energy per atom as compared to pristine Al₁₃⁻ cluster. Oxygen adsorption studies show that O₂ binds strongly in both atop and bridged modes on all the clusters, except for NbAl₁₂⁻, RuAl₁₂⁻, and ReAl₁₂⁻ clusters, where oxygen binding occurs only in the bridged mode. Additionally, the closed-shell clusters doped with Tc, Ta, Rh, and Ir exhibited exceptionally low spin excitation energy (SPE) values of 0.01, 0.20, 0.26, and 0.37 eV, respectively, as compared to the pristine Al cluster which showed a significantly higher SPE of 1.27 eV. The low SPE values suggest that these doped clusters will be effective for O₂ binding and activation. These findings provide fundamental insights into the structure and reactivity of doped Al₁₃⁻ clusters.