Structural classification of polyatomic molecules based on valence electron orbital radii: AB3 and A2B2 compounds

We classify the equilibrium structures of sp-bonded tetramers with schemes based on valence electron orbital radii. Valence electron orbital radii plots show the transition from planar to nonplanar geometries, and account for trends in bond angles, thus confirming the success previously obtained by Andreoni, Galli, and Tosi for AB2 molecules. © 1987 The American Physical Society.