Ionic to covalent bonding: a density functional theory study of linear and bent X2Y3 monomers (X = B, Al, Ga, In; Y = O, S, Se)

The results of hybrid density functional calculations are reported at the B3-LYP level using all-electron basis sets for Y-X-Y-X-Y (X = B, Al, Ga, In; Y = O, S, Se) species in their linear and bent structures.While Al2O3 is linear, In2O3 has both linear and bent ground-state structures.All other species have only bent structures as a minima.In2Se3 tends to be a shallow U-shaped structure.Al2O3, with the maximum X-Y electronegativity difference, has maximum ionic bonding.At the other extreme, B2Se3 has the least electronegativity difference and maximum X-Y covalent bonding.The natural charge analysis distinctively illustrates this by the polarization of charges between X and Y in the X2Y3 systems.The results of NBO analysis are also discussed.