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. A(l)2O(3), 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.