Abstract
The quest for "chemical accuracy" is becoming more and more demanded in the field of structure and kinetics of molecules at solid surfaces. In this paper, as an example, we focus on the barrier for hydrogen diffusion on a α-Al2O3(0001) surface, aiming for a couple cluster singles, doubles, and perturbative triples [CCSD(T)]-level benchmark. We employ the density functional theory (DFT) optimized minimum and transition state structures reported by Heiden, Usvyat, and Saalfrank [J. Phys. Chem. C 123, 6675 (2019)]. The barrier is first evaluated at the periodic Hartree-Fock and local Møller-Plesset second-order perturbation (MP2) level of theory. The possible sources of errors are then analyzed, which includes basis set incompleteness error, frozen core, density fitting, local approximation errors, as well as the MP2 method error. Using periodic and embedded fragment models, corrections to these errors are evaluated. In particular, two corrections are found to be non-negligible (both from the chemical accuracy perspective and at the scale of the barrier value of 0.72eV): the correction to the frozen core-approximation of 0.06eV and the CCSD(T) correction of 0.07eV. Our correlated wave function results are compared to barriers obtained from DFT. Among the tested DFT functionals, the best performing for this barrier is B3LYP-D3.
Highlights
Surfaces are natural and in many cases very efficient catalysts for various types of reactions
As an example, we focus on the barrier for hydrogen diffusion on a α-Al2O3(0001) surface, aiming for a CCSD(T)-level benchmark
In a recent publication,[2] some of us demonstrated that a hybrid-density functional theory (DFT) treatment, or MøllerPlesset second order perturbation theory (MP2), can deliver a more realistic barrier for hydrogen diffusion on aluminum oxide surfaces
Summary
Surfaces are natural and in many cases very efficient catalysts for various types of reactions. Standard computational protocols for surface reactions employ periodic super-cell models, treated with plane wave basis sets and density functional theory (DFT), within the generalized gradient approximation (GGA). There are some fully periodic implementations,[13,14] yet these are still very computationally demanding, especially for large unit cells, as in our case Another possible strategy is to employ representative finite clusters, either exclusively[15,16] or for correcting a low-level periodic treatment.[17,18,19,20,21,22,23,24,25,26,27,28] the applicability of this approach depends on the existence of clusters that can adequately mimic the parent solid. For the system under study here – aluminum oxide – construction of such clusters is highly problematic
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
