The effects of atom pyramidalization and square distribution on the stability of F_4F_6-(BN)_n polyhedrons

摘要

The structures and stability of F4F6-(BN)_n polyhedrons (n = 20-30) with the alternation of B and N atoms were studied with DFT method. The calculation results reveal that the atoms at square-square fusions with large pyramidalization angles are remarkably extruded out of the surfaces of (BN)n polyhedrons. The energetically favorable isomers do not contain square-square bonds and the energies of those isomers containing square-square bonds increase with the number of square-square bonds linearly, demonstrating that the energetically favorable structures of F_4F _6-(BN)_n polyhedrons satisfy the isolated square rule and square adjacency penalty rule. The atom pyramidalization determines the stability of the isomers. The binding energy is fitted to the numbers of vertices formed from different faces and a model is proposed to predict the relative stability of these polyhedral molecules.