A quantum chemical study of the structure of dodecasilsequioxane H12Si12O18

Quantum chemical B3LYP/cc-pVTZ, PBE0/cc-pVTZ, and MP2(full)/6-311G(d,p) methods are used to calculate the structural parameters of dodecasilsequioxane H₁₂Si₁₂O₁₈ and the H₁₂Si₁₂O ₁₈ ⁺ cation. According to DFT/cc-pVTZ calculations the energy of H₁₂Si₁₂O₁₈ (D _6h ) is 1.3–1.7 kcal/mol higher than the energy of H₁₂Si₁₂O₁₈ (D _2d ). A reduction of the basis set results in a greater energy difference of H₁₂Si₁₂O₁₈ isomers. For the cation ² B _2u and ² B ₁ electronic states are obtained, which correspond to symmetric equilibrium structures H₁₂Si₁₂O ₁₈ ⁺ (D _6h ) and (D ₂) respectively. For the He@H₁₂Si₁₂O₁₈ endocomplex the D _2d symmetry is obtained; for He₂@H₁₂Si₁₂O₁₈ the D _2h symmetry; and for H₂@H₁₂Si₁₂O₁₈ the D _6h symmetry.