Surface Adsorption from the Exchange-Hole Dipole Moment Dispersion Model

The accurate calculation of intermolecular interaction energies with density functional theory requires methods that include a treatment of long-range, nonlocal dispersion correlation. In this work, we explore the ability of the exchange-hole dipole moment (XDM) dispersion correction to model molecular surface adsorption. Adsorption energies are calculated for six small aromatic molecules (benzene, furan, pyridine, thiophene, thiophenol, and benzenediamine) and the four DNA nucleobases (adenine, thymine, guanine, and cytosine) on the (111) surfaces of the three coinage metals (copper, silver, and gold). For benzene, where the experimental reference data is most precise, the mean absolute error in the computed absorption energies is 0.04 eV. For the other aromatic molecules, the computed binding energies are found to be within 0.09 eV of the available reference data, on average, which is well below the expected experimental uncertainties for temperature-programmed desorption measurements. Unlike other dispersion-corrected functionals, adequate performance does not require changes to the canonical XDM implementation, and the good performance of XDM is explained in terms of the behavior of the exchange hole. Additionally, the base functional employed (B86bPBE) is also optimal for molecular studies, making B86bPBE-XDM an excellent candidate for studying chemistry on material surfaces. Finally, the noncovalent interaction (NCI) plot technique is shown to detect adsorption effects in real space on the order of tenths of an eV.利用密度泛函理论（density functional theory）精确计算分子间相互作用能时，需要能够处理长程非局域色散关联的方法。本研究探讨了交换孔偶极矩（exchange-hole dipole moment, XDM）色散校正方法对分子表面吸附过程的建模能力。我们针对三种铜族金属（铜、银、金）的(111)晶面，计算了六种小型芳香族分子（苯、呋喃、吡啶、噻吩、苯硫酚、苯二胺）以及四种DNA核碱基（腺嘌呤、胸腺嘧啶、鸟嘌呤、胞嘧啶）的吸附能。对于实验参考数据最为精确的苯体系，计算得到的吸附能平均绝对误差为0.04 eV。对于其余芳香族分子，计算得到的结合能与现有参考数据的平均偏差不超过0.09 eV，这一精度远低于程序升温脱附测量的预期实验不确定度。与其他色散校正泛函不同，XDM方法无需对标准实现方案进行修改即可获得优异性能，其良好表现可通过交换孔的行为特性得到解释。此外，本研究采用的基础泛函（B86bPBE）同样适用于分子体系研究，因此B86bPBE-XDM是研究材料表面化学过程的理想候选方法。最后，非共价相互作用（noncovalent interaction, NCI）绘图技术可用于探测实空间中量级为0.1 eV的吸附效应。