QM/MM modelling of the TS-1 catalyst using HPCx

We report a series of computations on the active site in Ti-substituted zeolites, specifically TS-1. Hybrid QM/MM methods based on density functional calculations using the BB1K functional and a valence force field are used to study the processes of hydrolysis of Ti-O-Si linkages and inversion of the TiO4 tetrahedra. The structural features of the resulting series of tetra- and tripodal Ti moieties are in good agreement with data from EXAFS studies. The suggestion is made that the tripodal species will dominate in hydrous conditions, and that this is likely to be the chemically active form. We have made extensive use of the massively parallel HPCx computer system for these investigations and outline some of the technical developments to the ChemShell software that were needed to support the study.