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Ab Initio Calculation of Rate Constants for Molecule-Surface Reactions with Chemical Accuracy.

Piccini G, Alessio M, Sauer J - Angew. Chem. Int. Ed. Engl. (2016)

Bottom Line: We present a divide-and-conquer strategy that departs from the potential energy surfaces obtained by standard density functional theory with inclusion of dispersion.The energies of the reactant and transition structures are refined by wavefunction-type calculations for the reaction site.Thermal effects and entropies are calculated from vibrational partition functions, and the anharmonic frequencies are calculated separately for each vibrational mode.

View Article: PubMed Central - PubMed

Affiliation: Institut für Chemie, Humboldt-Universität, Unter den Linden 6, 10099, Berlin, Germany.

No MeSH data available.


Unit‐cell view of the H‐MFI zeolite showing the embedded cluster used for the QM/QM calculations with the transition structure for the methylation of ethene at the active site. Aluminum blue, hydrogen white, oxygen red, silicon yellow. Non‐embedded framework atoms are shown in green.
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anie201601534-fig-0001: Unit‐cell view of the H‐MFI zeolite showing the embedded cluster used for the QM/QM calculations with the transition structure for the methylation of ethene at the active site. Aluminum blue, hydrogen white, oxygen red, silicon yellow. Non‐embedded framework atoms are shown in green.

Mentions: For direct comparison with experiment, apparent barriers were considered, that is, the energy difference between the transition structure and the methanol–catalyst complex with the alkene molecule in the gas phase, and the computational protocol proposed in Refs. 17 and 19 was applied. Figure 1 shows the crystallographic unit cell of the above zeolite with the transition structure for the methylation of ethene (a×b×c=20.16×20.03×13.47 Å3), which contains about 300 atoms. Periodic boundary conditions were applied to the DFT calculations, which used plane waves20 and applied the PBE functional21 with Grimme's semi‐empirical “D2” dispersion term.22 The subtractive scheme was used to obtain single‐point energies at the hybrid MP2/CBS:PBE+D2 level of theory.19 High‐level (MP2) calculations were performed on the cluster models shown in the Supporting Information, Figure S1 with the TURBOMOLE code.23 Gaussian basis sets with complete basis set (CBS) extrapolation were applied. Counterpoise corrections were made to account for the basis‐set superposition error, and Table S2 shows the individual energy contributions. The difference between the CCSD(T) coupled‐cluster and MP2 energies were evaluated for the smaller models shown in Figure S2.


Ab Initio Calculation of Rate Constants for Molecule-Surface Reactions with Chemical Accuracy.

Piccini G, Alessio M, Sauer J - Angew. Chem. Int. Ed. Engl. (2016)

Unit‐cell view of the H‐MFI zeolite showing the embedded cluster used for the QM/QM calculations with the transition structure for the methylation of ethene at the active site. Aluminum blue, hydrogen white, oxygen red, silicon yellow. Non‐embedded framework atoms are shown in green.
© Copyright Policy - creativeCommonsBy-nc-nd
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834608&req=5

anie201601534-fig-0001: Unit‐cell view of the H‐MFI zeolite showing the embedded cluster used for the QM/QM calculations with the transition structure for the methylation of ethene at the active site. Aluminum blue, hydrogen white, oxygen red, silicon yellow. Non‐embedded framework atoms are shown in green.
Mentions: For direct comparison with experiment, apparent barriers were considered, that is, the energy difference between the transition structure and the methanol–catalyst complex with the alkene molecule in the gas phase, and the computational protocol proposed in Refs. 17 and 19 was applied. Figure 1 shows the crystallographic unit cell of the above zeolite with the transition structure for the methylation of ethene (a×b×c=20.16×20.03×13.47 Å3), which contains about 300 atoms. Periodic boundary conditions were applied to the DFT calculations, which used plane waves20 and applied the PBE functional21 with Grimme's semi‐empirical “D2” dispersion term.22 The subtractive scheme was used to obtain single‐point energies at the hybrid MP2/CBS:PBE+D2 level of theory.19 High‐level (MP2) calculations were performed on the cluster models shown in the Supporting Information, Figure S1 with the TURBOMOLE code.23 Gaussian basis sets with complete basis set (CBS) extrapolation were applied. Counterpoise corrections were made to account for the basis‐set superposition error, and Table S2 shows the individual energy contributions. The difference between the CCSD(T) coupled‐cluster and MP2 energies were evaluated for the smaller models shown in Figure S2.

Bottom Line: We present a divide-and-conquer strategy that departs from the potential energy surfaces obtained by standard density functional theory with inclusion of dispersion.The energies of the reactant and transition structures are refined by wavefunction-type calculations for the reaction site.Thermal effects and entropies are calculated from vibrational partition functions, and the anharmonic frequencies are calculated separately for each vibrational mode.

View Article: PubMed Central - PubMed

Affiliation: Institut für Chemie, Humboldt-Universität, Unter den Linden 6, 10099, Berlin, Germany.

No MeSH data available.