Atomistic understanding of complex surface phenomena such as heterogeneous catalysis or storage and separation of energy-relevant gases in nanoporous materials (zeolites; metal-organic frameworks, MOFs) requires knowledge about reaction energies and energy barriers for elementary steps. This is difficult to obtain from experiment since the number of possible chemical, adsorption/desorption, and diffusion steps coupled to complex reaction networks is large, and so is the number of possible surface sites. Here is an important role of quantum chemistry which can provide rate and equilibrium constants for elementary steps "ab initio." To be useful, the predictions have to reach chemical accuracy (4 kJ/mol) which is difficult to achieve because realistic models of the surface systems may comprise of the order of a thousand atoms. While density functional theory (DFT) as a rule cannot be trusted to yield results within chemical accuracy limits, methods that are accurate enough (Coupled Cluster with Single, Double, and perturbative Triple Substitution, CCSD(T)) cannot be applied because of their exponential scaling with system size. This Account presents a hybrid high-level-low-level quantum method that combines DFT with dispersion for the full periodic system with second order Møller-Plesset perturbation theory (MP2) for the reaction site within a mechanical embedding scheme. In addition, to check if MP2 is accurate enough, we calculate Coupled Cluster (CC) corrections with Single, Double, and perturbatively treated Triple substitutions (CCSD(T)) for sufficiently small models of the reaction site. This multilevel hybrid MP2:DFT-D+ΔCC method is shown to yield chemical accuracy for a set of 12 molecule-surface interaction systems for which reliable experimental data are available. For CO/MgO(001), the history of the experiment-theory comparison illustrates two problems: (i) Do experiment and theory look at the same surface site? (ii) Does theory calculate the same quantity as derived from experiment? The hybrid MP2:DFT-D+ΔCC data set generated includes the MgO(001) surface, the Mg2(dobdc) metal-organic framework, and the proton forms of the CHA and MFI zeolites interacting with the H2, N2, CO, CO2, CH4, and C2H6 molecules. It serves two purposes. First, it will be useful for testing density functionals with respect to their performance for molecule-surface interactions. Second, it establishes the hybrid MP2:DFT-D+ΔCC method as a reliable and powerful tool for ab initio predictions of adsorption and reaction energies as well as energy barriers when testing reaction mechanisms. For adsorption of small molecules in MOFs, isotherm predictions have reached a level of accuracy that deviations between theoretical predictions and experiments indicate sample imperfections. For elementary steps of the industrially important methanol-to-olefin process, our hybrid MP2:PBE+D+ΔCC calculations yield rate constants in agreement with experiment within chemical accuracy limits, finally achieving for molecule-surface reactions which was possible so hitherto only for gas phase reactions involving not more than 10 atoms.

中文翻译：

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具有化学精度的分子表面相互作用的从头算计算。

对复杂表面现象的原子学理解，例如纳米多孔材料（沸石；金属有机骨架，MOF）中的多相催化或能量相关气体的存储和分离，需要有关基本步骤的反应能和能垒的知识。这很难从实验中获得，因为耦合到复杂反应网络的可能的化学，吸附/解吸和扩散步骤的数量很大，并且可能的表面部位的数量也很大。这是量子化学的重要作用，它可以为基本步骤“从头开始”提供速率和平衡常数。为了有用，预测必须达到化学精度（4 kJ / mol），这是很难实现的，因为表面系统的实际模型可能包含约1000个原子。虽然通常不能相信密度泛函理论（DFT）可以在化学精度范围内得出结果，但由于其准确性高，因此无法应用足够准确的方法（具有单，双和扰动三重取代的耦合簇，CCSD（T））与系统大小成指数比例缩放。该帐户提出了一种混合的高级-低级量子方法，该方法将DFT与色散结合起来用于整个周期系统，并为机械嵌入方案中的反应部位提供了二阶Møller-Plesset微扰理论（MP2）。另外，要检查MP2是否足够准确，我们为反应位点的足够小模型计算了具有单，双和经扰动处理的三重取代（CCSD（T））的耦合簇（CC）校正。此多级混合MP2：结果表明，DFT-D +ΔCC方法可对一组12个分子-表面相互作用系统产生化学准确度，而该系统可获得可靠的实验数据。对于CO / MgO（001），实验理论比较的历史说明了两个问题：（i）实验和理论是否看待相同的表面位点？（ii）理论计算得出的数量是否与实验得出的数量相同？生成的混合MP2：DFT-D +ΔCC数据集包括MgO（001）表面，Mg2（dobdc）金属-有机骨架以及CHA和MFI沸石与H2，N2，CO，CO2相互作用的质子形式，CH4和C2H6分子。它有两个目的。首先，对于测试密度泛函在分子表面相互作用方面的性能，这将是有用的。其次，它建立了混合MP2：DFT-D +ΔCC方法是一种可靠而强大的工具，可在测试反应机理时从头开始预测吸附和反应能以及能垒。对于MOF中小分子的吸附，等温线预测已达到准确度水平，理论预测与实验之间的偏差表明样品存在缺陷。对于工业上重要的甲醇制烯烃工艺的基本步骤，我们的混合MP2：PBE + D +ΔCC在化学精度范围内与实验一致地计算出产率常数，最终实现了分子表面反应，这迄今为止可能仅适用于气相反应涉及不超过10个原子。等温线预测的准确性已达到一定水平，即理论预测与实验之间的偏差表明样品存在缺陷。对于工业上重要的甲醇制烯烃工艺的基本步骤，我们的混合MP2：PBE + D +ΔCC在化学精度范围内与实验一致地计算出产率常数，最终实现了分子表面反应，这迄今为止可能仅适用于气相反应涉及不超过10个原子。等温线预测的准确性已达到一定水平，即理论预测与实验之间的偏差表明样品存在缺陷。对于工业上重要的甲醇制烯烃工艺的基本步骤，我们的混合MP2：PBE + D +ΔCC在化学精度范围内与实验一致地计算出产率常数，最终实现了分子表面反应，这迄今为止可能仅适用于气相反应涉及不超过10个原子。