Structure- and Size-Dependent Properties of BnCu20/- (n = 2-14) Clusters: DFT Calculations.

The structural and stability properties of two Cu atoms doped boron clusters (B_nCu₂ with n = 2-14) are investigated by a genetic algorithm method in combination with density functional theory (DFT) calculations. The lowest energy clusters of neutral clusters (B_nCu₂⁰) adopt two-dimensional (2D) structures for n ≤ 6, 10, and 12. For anionic clusters (B_nCu₂^-) the structural patterns are similar, however, the Cu atoms tend to pair up and form dimers instead of islands. The stability of the clusters, evaluated through the binding energy, second-order energy difference, and ionization energy, reveals that the neutral clusters B₄Cu₂⁰, B₆Cu₂⁰, and B₈Cu₂⁰, as well as the anionic clusters B₉Cu₂^-, B₁₁Cu₂^-, and B₁₃Cu₂^-, have greater chemical and thermodynamic stability than their neighbors in size. The favored structures for these clusters are found to be related with stable boron motifs which correspond to magic clusters. Moreover, the Cu₂-B_n interaction of the clusters were analyzed using the Energy Decomposition Analysis (EDA) and Natural Bond Order (NBO) charges, which supported the current findings. According to the AdNDP analyses, the stability of the clusters can be understood by the presence of delocalized sigma orbitals along the boron backbone.