Configurational inversion of the tetrahedral molecules CH4, SiH4, and GeH4 Original Research Article

We discuss from computed density functional theory energies as well as Hartree–Fock, Kohn–Sham, and their hybrid combinations how the configurational inversion of the tetrahedral AH4 molecules CH4, SiH4, and GeH4 takes place. In contrast to methane, the configurational inversion of which can occur via a Cs transition state, both silane and germane can undergo configurational inversion via a square-planar D4h transition state. The activation energy for the inversion is 109.4, 88.6, and 93.7 kcal/mol in methane, silane, and germane, respectively, at the B3LYP/6-311G** level of theory. Walsh diagrams are analyzed to increase our knowledge with respect to the configurational inversion of these tetrahedral molecules in terms of one-electron orbitals. The way of configurational inversion is strictly determined by which of the “nonbonding” a2u and b1g orbitals in the D4h structures is occupied by a pair of electrons.