Molecular structures of M ₂N ₂ ^2- (M and N = B, Al, and Ga) clusters using the gradient embedded genetic algorithm

Al ₄ ^2- was the first discovered σ + π aromatic all-metal cluster. In the present work we analyze the molecular structure, relative stability, and aromaticity of lowest-lying isomers of related M ₂N ₂ ^2- (M and N = B, Al, and Ga) clusters, with special emphasis devoted to the cis (C _2v) and trans (D _2h) isomers of the M ₂N ₂ ^2- clusters. For such purpose, we start by performing the search of the global minimum for each cluster through the Gradient Embedded Genetic Algorithm (GEGA). Energy decomposition analyses and the calculated magnetic- and electronic-based aromaticity criteria of the lowest-lying isomers help to understand the nature of the bonding and the origin of the stability of the global minima. Such methodology should allow guiding future molecular design strategies. This journal is