DFT GGA errors in NO chemisorption energies on (111) transition metal surfaces: Possible origins and correction schemes
Here we investigate whether well known DFT GGA errors in predicting the chemisorption energy $E_{\rm chem} of CO on transition metal surfaces manifest in analogous NO chemisorption systems. To verify the occurrence of DFT GGA overestimation of the back donation mechanism in NO Chemisorption, we use electronic structure analysis to show that the partially filled molecular NO 2$\pi^ orbital rehybridizes with the transition metal $d$ band to form new bonding and anti bonding states. We relate the back donation charge transfer associated with chemisorption to the promotion of an electron from the 5$\sigma$ orbital to the 2$\pi^ orbital in the gas phase NO G${2}\Sigma^ \leftarrow \rm{X}{2}\Pi$ excitation. We establish linear relationships between $E_{\rm chem} and \Delta E_{\rm G\leftarrow X} and go on to formulate an $E_{\rm chem} correction scheme in the style of Mason \it et al. [Physical Review B \bf 69} 161401(R) We apply the NO $E_{\rm chem} correction method to the (111) surfaces of Pt, Pd, Rh, and Ir, with NO chemisorption modeled at a coverage of 0.25 ML. We note that both the slope of $E_{\rm chem} \it vs. \Delta E_{\rm G\leftarrow X} and the dipole moment depend strongly on adsorption site for each metal, and we use this fact to construct an approximate correction scheme which we go on to test using NO/Pt(100) chemisorption.