Understanding the Acidic Properties of the Amorphous Hydroxylated Silica Surface

Amorphous silica is an intrinsic challenging system to study. In the last decades, some particular chemical properties have been discovered and described, but their description and understanding at the molecular level are experimentally difficult. Therefore, theoretical quantum chemical methods and descriptors, combined with experimental input, are a very appropriate set up to tackle this topic. In this study, the acidity of silanol groups of amorphous silica in hydrated conditions is investigated. Special attention has been drawn to the chemical shift, but also Bader charges, and vibrational frequencies with their intensities. The known bimodal acidity behavior was recovered and rationaliz…