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| Abstract |
The Hartree-Fock level optimizations were done on the octasilsesquioxane（Si_8O_12H_8）of double four-ring（D4R）cage， the trapped atomic hydrogen in D4R cage（H＠D4R），and the transition state of detrapping... process from H＠D4R to D4R． Both of D4R and H＠D4R were optimized with O_h molecular symmetry and the cage conformations in D4R and H＠D4R were very similar． On H＠D4R trapped H atom was located at the center of D4R cage． From one point calculations with Mφller-Plesset Second-Order perturbation（MP2）1evel on each optimized structure， the activation and reaction energies of this detrapping process were +106.3 and -16.1kJ/mo1， respectively． The value of activation energy was in good agreement with Stösser’s experimental data（+109.6±3.lkJ/mol）． The small interaction between D4R cage and trapped H atom in H＠D4R was represented by Singly Occupied Molecular Orbital（SOMO）［8a_1g］of H＠D4R which was constructed from antレbonding interaction between Lowest Unoccupied Molecular Orbital（LUMO）［8a_lg］of D4R and 1s radical orbital of trapped H atom． On the transition state， the positions of all Si atoms were unchanged， and four O atoms in the single four-ring were displaced so as to open one of one-side windows on D4R cage from the influence of detrapping of H atom．show more
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