Alkane Adsorption on Pt(111): the Dispersion Interaction on Metal Surfaces*

Alkane adsorption on metal surfaces occurs primarily through the vdW-type dispersion interaction. This is unaccounted for by most DFT methods, with the exception of the vdW-functionals.^1-2 Instead, corrective terms must be added or higher-level methods used. However, this is a challenge for periodic systems, such as metal surfaces, where few high-level methods can be applied without prohibitive cost.

The Random Phase Approximation (RPA) is one such suitable method.³ Nonetheless, it remains an expensive approach, requiring careful convergence to obtain meaningful results. However, the adsorption energy can be obtained to within chemical accuracy (±4 kJ mol^-1). This can be matched for methane by DFT with some dispersion corrections (DFT+D) but this disappears with increasing alkane chain length. In the future, a hybrid QM:QM method will be used to correct periodic DFT calculations with RPA.⁴ This will provide high accuracy, while being much cheaper than full periodic RPA.

1. Grimme, S., et al., Chem. Rev. 2016, 116 (9), 5105
2. Dion, M., et al., PRL 2004, 92 (24), 246401
3. Ren, X., et al., J. Mat. Sci. 2012, 47 (21), 7447
4. Alessio, M., et al., PCCP 2018, 20 (15), 9760