The nature of NOx species on BaO(100): an ab initio molecular dynamics study

The dynamics of NO(x) species adsorbed on BaO(100) have been investigated with ab initio molecular dynamics simulations at a temperature of 300 degrees C. Nitrites are found to continuously interconvert between different adsorption configurations. For both nitrites and nitrates, diffusion events between anion sites are observed. These findings support the use of spillover mechanisms often postulated in mechanistic models of catalysts based on the NO(x)() storage and reduction concept. The large number of possible adsorption configurations are reflected in broad calculated vibrational signatures. These results explain the corresponding property observed in experimental infrared measurements of NO(x)() species on BaO. The dynamic response of the BaO(100) surface is found to strongly depend on the nature of the surface-adsorbate interaction. The largest distortions are predicted for nitrite adsorption.