The article "CO Chemisorption at Metal Surfaces and Overlayers" by Hammer, Morikawa, and Nørskov presents a comprehensive database of ab initio calculations of CO chemisorption energies on various metal surfaces and overlayers. The authors develop a simple model that describes the interaction between the metal's d states and the CO 2π* and 5σ states, which are renormalized by the metal's sp continuum. This model explains the strong correlation between the CO chemisorption energy and the surface core level shift, as observed by Rodriguez and Goodman. The model is validated through extensive DFT-GGA calculations, demonstrating its ability to predict the trends in CO chemisorption energies across different metals and overlayers. The key parameter determining the strength of the bonding is the energy of the center of the metal d band, which can be obtained from spectroscopic methods. The model also captures the shifts in CO chemisorption energy from single crystal surfaces to overlayers, providing a quantitative understanding of the electronic factors involved in CO-metal bonding.The article "CO Chemisorption at Metal Surfaces and Overlayers" by Hammer, Morikawa, and Nørskov presents a comprehensive database of ab initio calculations of CO chemisorption energies on various metal surfaces and overlayers. The authors develop a simple model that describes the interaction between the metal's d states and the CO 2π* and 5σ states, which are renormalized by the metal's sp continuum. This model explains the strong correlation between the CO chemisorption energy and the surface core level shift, as observed by Rodriguez and Goodman. The model is validated through extensive DFT-GGA calculations, demonstrating its ability to predict the trends in CO chemisorption energies across different metals and overlayers. The key parameter determining the strength of the bonding is the energy of the center of the metal d band, which can be obtained from spectroscopic methods. The model also captures the shifts in CO chemisorption energy from single crystal surfaces to overlayers, providing a quantitative understanding of the electronic factors involved in CO-metal bonding.