NEUTRON SPECTROSCOPY OF WATER ADSORBED AT AEROSIL

Computational and real neutron scattering experiments are presented. The computational one is based on the modern cluster approximation of a computational chemistry. A few models for water molecule deposition at the aerosil surface are considered. The core and surface of aerosil are simulated by clusters with up to 150 atoms. The active centre is selected. It is shown that water molecules join willingly to a silicon atom forming a group of four coordinated molecules. Additionally these molecules attract other ones forming a “subcluster” (up to 8–10 molecules) bound to one centre. Optimized structure, electron density distribution, binding energy and force field constants are calculated. Basing on these data weighted densities of vibrational states are obtained. The results are in good agreement with experimental inelastic neutron scattering spectra recorded at 10, 80 and 290 K at Dubna for aerosil A380OHH2O and A380ODD2O (A380 means aerosil with a specific area of 380 (m2 g−1).