A periodic DFT study of water and ammonia adsorption on anatase TiO2 (001) slab

Water and ammonia adsorption mechanisms on anatase TiO₂ (001) slab surface are investigated by means of periodic DFT approach. Molecular and dissociative adsorption energies for water are calculated to be ? 15 kcal/mol and ? 32 kcal/mol, respectively. Similarly, molecular and dissociative adsorption energies of ammonia on the same surface are found as ? 25 kcal/mol and ? 20 kcal/mol. A reverse result in this order is reached for the previous case of ONIOM cluster study (? 23 kcal/mol and ? 37 kcal/mol, respectively). The vibration frequency values are computed for the optimized geometries of adsorbed water and ammonia molecules on anatase TiO₂ (001) slab surface and compared with the values reported in the literature.