First-principles extrapolation method for accurate CO adsorption energies on metal surfaces

Abstract

We show that a simple first-principles correction based on the difference between the singlet-triplet CO excitation energy values obtained by DFT and high-level quantum chemistry methods yields accurate CO adsorption properties on a variety of metal surfaces. We demonstrate a linear relationship between the CO adsorption energy and the CO singlet-triplet splitting, similar to the linear dependence of CO adsorption energy on the energy of the CO 2$\pi$* orbital found recently {[Kresse {\em et al.}, Physical Review B {\bf 68}, 073401 (2003)]}. Converged DFT calculations underestimate the CO singlet-triplet excitation energy $\Delta E_{\mathrm{S}-\mathrm{T}}$, whereas coupled-cluster and CI calculations reproduce the experimental $\Delta E_{\mathrm{S}-\mathrm{T}}$. The dependence of $E_{\mathrm{chem}}$ on $\Delta E_{\mathrm{S}-\mathrm{T}}$ is used to extrapolate $E_{\mathrm{chem}}$ for the top, bridge and hollow sites for the (100) and (111) surfaces of Pt, Rh, Pd and Cu to the values that correspond to the coupled-cluster and CI $\Delta E_{\mathrm{S}-\mathrm{T}}$ value. The correction reproduces experimental adsorption site preference for all cases and obtains $E_{\mathrm{chem}}$ in excellent agreement with experimental results.

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