Benchmarking van der Waals Density Functionals with Experimental Data: Potential Energy Curves for H2 Molecules on Cu(111), (100), and (110) Surfaces

TL;DR

This paper benchmarks van der Waals density functionals against experimental data for H2 molecules on Cu surfaces, showing that vdW-DF2 closely matches experimental potential energy curves and analyzing the effects of different exchange functionals.

Contribution

It provides a comparative analysis of vdW-DF2, DFT-D3, and TS-vdW functionals against experimental data for H2 on copper surfaces, highlighting the accuracy of vdW-DF2.

Findings

vdW-DF2 closely matches experimental potential energy curves

Backscattering barrier depends on exchange-functional choice

DFT-D3 and TS-vdW show deviations from experimental data

Abstract

Detailed physisorption data from experiment for the H_2 molecule on low-index Cu surfaces challenge theory. Recently, density-functional theory (DFT) has been developed to account for nonlocal correlation effects, including van der Waals (dispersion) forces. We show that the functional vdW-DF2 gives a potential-energy curve, potential-well energy levels, and difference in lateral corrugation promisingly close to the results obtained by resonant elastic backscattering-diffraction experiments. The backscattering barrier is found selective for choice of exchange-functional approximation. Further, the DFT-D3 and TS-vdW corrections to traditional DFT formulations are also benchmarked, and deviations are analyzed.