Ab initio molecular dynamics simulation of the interaction between water and Ti in zeolitic systems

We present the results of ab initio molecular dynamics simulations on titanium offretite. The aim of this work is to investigate at a microscopic level the room temperature behavior of titanium inserted into a fully periodic zeolitic framework in dry and hydrated conditions. Structural analysis indicates that titanium, at low water loading, is tetrahedrally coordinated by framework oxygens only. On the other hand, at higher loading, when water molecules are activated via hydrogen bonding, they interact with the Ti site, leading to an increase of the Ti coordination number up to 5. The insertion of a Ti center causes only moderate and local distortions to the silicate framework. Features due to Ti in the calculated vibrational spectra are in line with IR and Raman experiments.