Density Functional Theory for Molecule–Metal Surface Reactions: When Does the Generalized Gradient Approximation Get It Right, and What to Do If It Does Not

Abstract

While density functional theory (DFT) is perhaps the most used electronic structure theory in chemistry, many of its practical aspects remain poorly understood. For instance, DFT at the generalized gradient approximation (GGA) tends to fail miserably at describing gas-phase reaction barriers, while it performs surprisingly well for many molecule–metal surface reactions. GGA-DFT also fails for many systems in the latter category, and up to now it has not been clear when one may expect it to work. We show that GGA-DFT tends to work if the difference between the work function of the metal and the molecule’s electron affinity is greater than ∼7 eV and to fail if this difference is smaller, with sticking of O 2 on Al(111) being a spectacular example. Using dynamics calculations we show that, for this system, the DFT problem may be solved as done for gas-phase reactions, i.e., by resorting to hybrid functionals, but using screening at long-range to obtain a correct description of the metal. Our results suggest the GGA error in the O 2 + Al(111) barrier height to be functional driven. Our results also suggest the possibility to compute potential energy surfaces for the difficult-to-treat systems with computationally cheap nonself-consistent calculations in which a hybrid functional is applied to a GGA density.

From Behavior of Water on Hydrophobic Graphene Surfaces to Ultra-Confinement of Water in Carbon Nanotubes

“…This implies a more rigorous understanding of the spin (charges) density redistribution induced by the interaction of water entities with carbon structures. Although it is frequently used in the description of the electronic structure of a system, DFT based on the generalized gradient approximation has certain limitations, in particular for the modeling of chemical reactions [ 58 ] and the estimation of gas-phase energy barriers [ 59 ]. DFT-GGA may also not work well for many molecule–metal surface reactions and for van der Waals adsorption on surfaces [ 60 ].…”

Computational approaches to dissociative chemisorption on metals: towards chemical accuracy

“…ref. [348][349][350], and a screened hybrid DF has already been used in dynamics calculations on O 2 + Al( 111) 351 (see below). The B3LYP DF is the best known global hybrid DF 352 in which the exchange energy is a mixture of exact exchange (20%) and GGA exchange, 313 and GGA correlation 353 (the DF is therefore called a hybrid GGA DF).…”

“…Very recently QCT calculations have been performed 351 on O 2 + Al(111) that used the mGGA MS RPBEl DF 152 discussed earlier and the screened hybrid HSE03-1/3X DF. The HSE03-1/ 3X DF is based on the HSE03 DF 692,693 with the maximum fraction of exact exchange increased from 1/4 to 1/3.…”

Chemical dynamics from the gas‐phase to surfaces

“…It has recently been suggested that for reactions where the difference between the surface' work function and the electron affinity of the adsorbate is smaller than 7 eV, DFT-GGA calculations of barrier heights may be unreliable. 371 As seen in Figure 15, it is precisely under these conditions that electronically nonadiabatic coupling between 378 The influence of vibrational excitation on dissociative adsorption was first seen by changing the beam source temperature and seed gas to thermally excite CH 4 vibrations. 380,381 This influence of vibration is more cleanly seen with laser pre-excitation of the molecule, where a molecular beam of methane with controlled translational energy is excited by a c. w. infrared laser with high power and coherence producing selected vibrational states.…”

“…While the research on this reaction, so far, is no success story, it is without doubt one of the most interesting for future study. It has recently been suggested that for reactions where the difference between the surface’ work function and the electron affinity of the adsorbate is smaller than 7 eV, DFT‐GGA calculations of barrier heights may be unreliable 371 . As seen in Figure 15, it is precisely under these conditions that electronically nonadiabatic coupling between adsorbate nuclear motion and the solids EHPs may become important.…”