Silanol as a model for the free hydroxyl of amorphous silica: Ab initio calculations of the interaction with formaldehyde

✍ Scribed by P. Ugliengo; V.R. Saunders; E. Garrone

• Publisher: Elsevier Science
• Year: 1990
• Tongue: English
• Weight: 575 KB
• Volume: 169
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(90)85638-s

✦ Synopsis

Literature vibrational data concerning the interaction of formaldehyde with the isolated hydroxyl of amorphous silica are compared with the results of ab initio calculations by both the Hartree-Fock and correlated through perturbative technique (MP2 and MP3). Silanol H$iOH is chosen to mimic the silica free hydroxyl: H2C0 acts as H-acceptor. Calculated properties are the binding energy, vibrational spectrum in the harmonic approximation and free enthalpy of interaction. Excellent agreement with experiment is found. To characterize the intermolecular motions, a significant section of the intermolecular-potential hypersurface has been calculated; these results are so extremely flat as to render ditticult the definition of proper normal modes. The' comparison with the appropriate gas-phase complexes of formaldehyde shows that the acidity of H,SiOH is intermediate between HCI and HF.