Chemically accurate adsorption energies for methane and ethane monolayers on the MgO(001) surface

Abstract

A hybrid QM:QM method that combines MP2 as high-level method on cluster models with density functional theory (PBE+D2) as low-level method on periodic models is applied to adsorption of methane and ethane on the MgO(001) surface for which reliable experimental desorption enthalpies are available. Two coverages are considered, monolayer (every second Mg2+ ion occupied) and one quarter coverage (one of eight Mg2+ ions occupied). Structure optimizations are performed at the hybrid MP2:(PBE+D2) level, with the MP2 energies and forces counterpoise corrected for basis set superposition error and extrapolated to the complete basis set limit. For the MP2 calculations on the adsorbate monolayer a two-body expansion of the lateral molecule-molecule interactions is applied. Higher order correlation effects are evaluated at the hybrid MP2:(PBE+D2) equilibrium structures as coupled cluster [CCSD(T)] - MP2 differences adopting smaller basis sets. The final adsorption energies obtained for monolayer coverage are -14.0 ± 1.0 and -23.3 ± 0.6 kJ mol-1 for CH4·MgO(001) and C2H6·MgO(001), respectively. They agree within 1 kJ mol-1 - well within chemical accuracy limits - with reference energies of -15.0 ± 0.6 and -24.4 ± 0.6 kJ mol-1, respectively. The latter have been derived from measured desorption enthalpy barriers, taking zero-point vibrational energy (ZPVE) and thermal enthalpy contributions into account.

Partial Oxidation of Methanol on the Fe3O4(111) Surface Studied by Density Functional Theory

“…Admittedly, these differences in adsorption energies of D a and D b are small and amount to about 5 kJ/mol only. It would be interesting to assess these values either with functionals on fifth rung of the Jacob’s ladder, like the random phase approximation (see, for instance, ref ), or with post-HF wave function-based methods using embedding techniques or cluster models (see, e.g., refs and ).…”

Predicting adsorption selectivities from pure gas isotherms for gas mixtures in metal–organic frameworks

“…Chemical accuracy has been achieved for electronic energies by employing a quantum chemical hybrid method that uses Møller-Plesset second order perturbation theory (MP2) 39 at the adsorption site and DFT+dispersion (PBE+D2) for the full periodic structures. [40][41][42][43] For a smaller model of the adsorption site calculations are performed with Coupled Cluster theory, CCSD(T). 39 Thermal effects and entropies for CO and N 2 adsorption are obtained from vibrational partition functions with the anharmonic vibrational energies calculated for each vibrational mode separately.…”

Interaction of C3–C5Alkenes with Zeolitic Brønsted Sites: π-Complexes, Alkoxides, and Carbenium Ions in H-FER

“…Aiming for chemical accuracy (4.2 kJ/mol), in this work we perform hybrid MP2:(PBE+D2)+ΔCCSD­(T) calculations ,,,− to determine relative stabilities of all possible intermediates of propene, butene, and pentene isomers in H-FER (proton form of ferrierite), including π-adsorption complexes, alkoxides, and carbenium ions. This method has been shown to yield chemical accuracy for energy barriers and adsorption energies .…”