Here we investigate whether well-known DFT-GGA errors in predicting CO chemisorption on transition metal surfaces also manifest in NO/metal chemisorption systems. In particular, we use electronic structure analysis to show that the partially filled NO 2p* orbital rehybridizes with the transition metal d-band to form new bonding and anti-bonding states. We relate the back-donation of metal d-electrons into the 2p*-surface derived bonding state to the promotion of an electron from the 5s orbital to the 2p* orbital in a gas-phase NO doublet-doublet excitation. Our study demonstrates that the chemisorption energies of NO on transition metal surfaces depend on the predicted value of the NO excitation energy, for which we achieve variation by using different sets of N and O pseudopotentials. We obtain linear relationships in chemisorption energy as a function of NO excitation energy, and then use the experimental excitation energy as a calibration point to arrive at corrected chemisorption energies. We apply this method to a variety of metal surfaces and NO adsorption sites with a surface coverage of 0.25 ML, and discuss how the corrected values may better explain higher coverage adsorption patterns reported in the literature. Finally, we note that both the slope of the chemisorption energy vs. NO excitation energy and the surface dipole moment of NO depend strongly on adsorption site but weakly on metal identity, and we use this fact to propose an approximate correction scheme based on the surface dipole moment.

Identifying and correcting for DFT-GGA errors in NO chemisorption energies on transition metal surfaces

246th National Meeting (2013)

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