Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611, USA.
J Chem Phys. 2012 Feb 7;136(5):054702. doi: 10.1063/1.3679167.
We investigated the molecular binding of n-alkanes on Pd(111) and PdO(101) using conventional density functional theory (DFT) and the dispersion-corrected DFT-D3 method. In agreement with experimental findings, DFT-D3 predicts that the n-alkane desorption energies scale linearly with the molecule chain length on both surfaces, and that n-alkanes bind more strongly on PdO(101) than on Pd(111). The desorption energies computed using DFT-D3 are slightly higher than the measured values for n-alkanes on Pd(111), though the agreement between computation and experiment is a significant improvement over conventional DFT. The measured desorption energies of n-alkanes on PdO(101) and the energies computed using DFT-D3 agree to within better than 2.5 kJ/mol (< 5%) for chain lengths up to n-butane. The DFT-D3 calculations predict that the molecule-surface dispersion energy for a given n-alkane is similar in magnitude on Pd(111) and PdO(101), and that dative bonding between the alkanes and coordinatively unsaturated Pd atoms is primarily responsible for the enhanced binding of n-alkanes on PdO(101). From analysis of the DFT-D3 results, we estimate that the strength of an alkane η(2)(H, H) interaction on PdO(101) is ~16 kJ/mol, while a single η(1) H-Pd dative bond is worth about 10 kJ/mol.
我们使用传统密度泛函理论（DFT）和色散校正的 DFT-D3 方法研究了 n-链烷烃在 Pd(111)和 PdO(101)上的分子结合。与实验结果一致，DFT-D3 预测 n-链烷烃的脱附能与两种表面上的分子链长度呈线性关系，并且 n-链烷烃在 PdO(101)上的结合强度强于在 Pd(111)上。DFT-D3 计算的脱附能略高于 Pd(111)上 n-链烷烃的测量值，但与传统 DFT 相比，计算与实验之间的一致性有了显著提高。对于链长至正丁烷，实验测量的 n-链烷烃在 PdO(101)上的脱附能与 DFT-D3 计算的能量之间的一致性误差在 2.5 kJ/mol 以内（<5%）。DFT-D3 计算预测，对于给定的 n-链烷烃，其分子-表面色散能在 Pd(111)和 PdO(101)上的大小相似，并且烷烃和配位不饱和 Pd 原子之间的 dative 键主要负责增强 n-链烷烃在 PdO(101)上的结合。通过对 DFT-D3 结果的分析，我们估计在 PdO(101)上，烷烃的 η(2)(H, H)相互作用的强度约为 16 kJ/mol，而单个 η(1)H-Pd dative 键的价值约为 10 kJ/mol。
