Search

Abstract: We have calculated adsorption energies for N2O on the MgO (001) surface using periodic DFT calculations with the B3LYP functional and subsequent dispersion correction. Additionally a wave function-based correlation treatment at the MP2 level was performed. Whilst the B3LYP calculation failed to find a bond state, both the dispersion corrections and the MP2 treatment result in a significantly better description. The best agreement with experiment is obtained with a dispersion correction via the D3 scheme. The calculated binding energies are very similar for adsorption with the nitrogen or the oxygen end towards the surface, whilst calculated vibrational frequencies of adsorbed N2O match the experimental values better when assuming an O-down adsorption structure. [Copyright &y& Elsevier]

Abstract: We have characterised the Lewis acidity of unsaturated surface cations of MgF2 crystals using periodic calculations at the B3LYP level. The relative importance of low index surfaces was determined by calculating surface energies, and these surfaces were then probed by CO adsorption. We found that a MgF2 microcrystal should expose mainly (110), (100) and (101) surfaces in which the undercoordinated cations are fivefold coordinated. The adsorption energies and CO stretching frequencies are discussed with respect to the coordination number of surface cations and the stability of the surfaces and are compared to IR spectra from the literature. [Copyright &y& Elsevier]