Theoretical analysis of ethylene adducts to ion-bombarded porous silica

Density functional calculations have been performed on molecular models of silica defects and their C 2 H 4 adducts. The results are consistent with a previous experimental infrared characterization that was interpreted in terms of C 2 H 4 addition to the SiO 2 skeleton at both the oxygen-bridge and silicon-link vacancy defects produced by argon bombardment. The geometries and thermodynamical stabilities of the proposed species and other possible adducts have been evaluated. The calculated C  C, C  O and C–H stretching frequencies are in good agreement with the experimental values and confirm the validity of the previous interpretation, helping to clarify some unclear details.