Molecular structures of M2N22− (M and N = B, Al, and Ga) clusters using the gradient embedded genetic algorithm

Abstract

Al₄²⁻ 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 M₂N₂²⁻ (M and N = B, Al, and Ga) clusters, with special emphasis devoted to the cis (C_2v) and trans (D_2h) isomers of the M₂N₂²⁻ 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.