Ab initio Free Energy Calculations with Chemical Accuracy for Molecule-Surface Interactions

多相催化以及纳米多孔材料中能量相关气体的存储和分离的原子理解需要具有化学精度（4 kJ/mol）的大周期系统的自由能的量子力学从头算预测。我们已经表明，这可以通过以下方式实现：（i）使用混合高水平-低水平计算，将反应位点的精确波函数方法与完整（伪）周期系统上的较不精确但计算效率更高的密度泛函理论计算相结合;以及（ii）以负担得起的方式计算非谐振动能，以改善势能面的采样。这样的方法到目前为止还不存在。建议（1）开发一种强大且广泛适用的方法，该方法将免费提供给社区，冒着我们用于计算非谐性的近似值不适用于所有类型的表面结合的风险，并且关键的技术步骤-正常模式的曲线表示-不能充分自动化，（2）建立一个分子-表面相互作用的数据库，其与实验的熵和/或熵一致，因此适合于基准近似方法，以及（3）使用该方法获得选定应用中的基本步骤的动力学和热力学数据，例如，沸石催化以及金属有机骨架的气体储存和分离。

Atomistic understanding of heterogeneous catalysis as well as of storage and separation of energy-relevant gases in nanoporous materials requires the quantum mechanical ab initio prediction of free energies for large periodic systems with chemical accuracy (4 kJ/mol). We have shown that this can be achieved by (i) use of hybrid high level - low level calculations combining accurate wave-function methods for the reaction site with less accurate, but computationally more efficient density functional theory calculations on the full (pseudo) periodic system, and (ii) calculating anharmonic vibrational energies in an affordable way to improve the sampling of the potential energy surface. Such a method did not exist so far. It is proposed (1) to develop a robust and broadly applicable methodology that will be freely available to the community, taking the risk that the approximations we apply to calculate anharmonicities are not valid for all types of surface bonding and that a crucial technical step - curvilinear representation of normal modes - cannot be made sufficiently automatic, (2) to build a data base of molecule - surface interactions for which agreement is achieved with experimental enthalpies and/or entropies and which are, thus, suitable for benchmarking approximate methods, and (3) to use this methodology to obtain kinetic and thermodynamic data for elementary steps in selected applications, e.g., catalysis by zeolites as well as gas storage and separation by metal-organic frameworks.