Many-Body Methods for Surface Chemistry Come of Age: Achieving Consensus with Experiments

Abstract

The adsorption energy of a molecule onto the surface of a material underpins a wide array of applications, spanning heterogeneous catalysis, gas storage, and many more. It is the key quantity where experimental measurements and theoretical calculations meet, with agreement being necessary for reliable predictions of chemical reaction rates and mechanisms. The prototypical molecule–surface system is CO adsorbed on MgO, but despite intense scrutiny from theory and experiment, there is still no consensus on its adsorption energy. In particular, the large cost of accurate many-body methods makes reaching converged theoretical estimates difficult, generating a wide range of values. In this work, we address this challenge, leveraging the latest advances in diffusion Monte Carlo (DMC) and coupled cluster with single, double, and perturbative triple excitations [CCSD­(T)] to obtain accurate predictions for CO on MgO. These reliable theoretical estimates allow us to evaluate the inconsistencies in published temperature-programed desorption experiments, revealing that they arise from variations in employed pre-exponential factors. Utilizing this insight, we derive new experimental estimates of the (electronic) adsorption energy with a (more) precise pre-exponential factor. As a culmination of all of this effort, we are able to reach a consensus between multiple theoretical calculations and multiple experiments for the first time. In addition, we show that our recently developed cluster-based CCSD­(T) approach provides a low-cost route toward achieving accurate adsorption energies. This sets the stage for affordable and reliable theoretical predictions of chemical reactions on surfaces to guide the realization of new catalysts and gas storage materials.

Adsorption and vibrational spectroscopy of CO on the surface of MgO from periodic local coupled-cluster theory

“…where E int is the interaction energy between CO and MgO calculated with their respective geometries fixed to be those in the MgO+CO composite system, and ∆ geom is the geometry relaxation energy. Following ref 17, we use our DFT-determined ∆ geom (1.1 kJ/mol from PBE+D3, which is in good agreement with previous work 16,17,27 ) in eqn (1) and evaluate E int using correlated wavefunction methods. All wavefunction calculations are performed with the PySCF code.…”

“…Reference values of E ads can be derived from the desorption activation energy measured by temperature-programmed desorption experiments. [9][10][11] This was done earlier by Boese and Sauer 16 who obtained a reference value of −20.6 ± 2.4 kJ/mol based on the experimental work by Dohnálek et al, 11 and more recently by Shi and co-workers 17 who derived a modified value of −19.2±1.0 kJ/mol by averaging two experimental results. 9,11 A correct theoretical prediction of E ads , however, necessitates the use of correlated wavefunction methods.…”

“…Nonetheless, this has been proven a challenging computational task over the past two decades. 14,15 The major difficulty stems from the inherently weak yet correlated nature of surface-adsorbate interactions, which necessitates achieving sub-kJ/mol accuracy for reliable comparison with experiments [14][15][16][17] and development of accurate force fields for molecular dynamics. [18][19][20][21] The demanded high accuracy is typically out of reach by density functional theory 22 (DFT) whose performance can depend sensitively on the choice of approximate exchange-correlation functionals (especially because of self-interaction errors) and dispersion correction methods.…”

“…In this work, we focus on CO adsorption on the MgO (001) surface, which is an extensively studied model system for high levels of theory. 16,17,27,28 Recently, Shi and co-workers 17 applied coupled-cluster theory with singles, doubles, and perturbative triples 29 [CCSD(T)], commonly known as the "gold standard" of main-group quantum chemistry, within an embedded-cluster framework 30 to produce their best estimate of the adsorption energy, −19.2 ± 1.0 kJ/mol, which was in good agreement with that calculated by canonical periodic CCSD(T) and diffusion Monte Carlo, as well as the value estimated from temperatureprogrammed desorption experiments 11 (about −20.0 kJ/mol).…”

Comparing Self-Consistent GW and Vertex-Corrected G0W0 (G0W0Γ) Accuracy for Molecular Ionization Potentials

“…Accurate and computationally accessible simulation of molecules and solids is a major goal when developing new or improving existing computational approaches. Wave function methods such as coupled cluster method (CC) − and configuration interaction (CI) − have seen great success in modeling moderately sized molecules and solids with small unit cells. However, these ab initio simulations for larger and more complicated systems still remain extremely challenging, mainly due to the high computational scaling.…”