Departamento de Química Física y Analítica, Facultad de Química , Universidad de Oviedo , 33006 Oviedo , Spain.
Department of Chemistry , Dalhousie University , 6274 Coburg Road , Halifax , Nova Scotia B3H 4R2 , Canada.
J Chem Theory Comput. 2019 Sep 10;15(9):4933-4944. doi: 10.1021/acs.jctc.9b00550. Epub 2019 Aug 16.
The accurate calculation of relative lattice energies of molecular crystals is important in polymorph ranking and crystal structure prediction. Delocalization error has been shown to affect calculated intermolecular binding energies in DFT and is similarly expected to affect the lattice energies of some classes of molecular crystals. In this work, we explore the use of dispersion-corrected hybrid functionals in the planewave-pseudopotentials approach to reduce delocalization error. We combine several hybrid functionals with the exchange-hole dipole moment (XDM) model for dispersion and show that they generally outperform GGA functionals in the calculation of both gas-phase binding energies and molecular crystal lattice energies. We apply the resulting XDM-corrected functionals to four halogen-bonded crystals: Cl, Br, I, and ICl. GGA functionals severely overestimate their lattice energies, while hybrid functionals give accurate values. The preference of GGA functionals for monatomic structures in the Br and Cl crystals is also explained. Finally, we apply a recently developed method to calculate Bader's delocalization indices to examine the extent of intermolecular delocalization in the halogen molecular crystals. It is shown that intermolecular delocalization indices can be used to measure the strength of halogen bonds within the crystal, as well as detect the presence of delocalization error.
准确计算分子晶体的相对晶格能对于多晶型物排名和晶体结构预测非常重要。离域误差已被证明会影响 DFT 中计算的分子间结合能，预计同样会影响某些类别的分子晶体的晶格能。在这项工作中，我们探索了在平面波赝势方法中使用色散校正杂化泛函来减少离域误差。我们将几种杂化泛函与色散的交换空穴偶极矩（XDM）模型相结合，结果表明它们通常在计算气相结合能和分子晶体晶格能方面优于 GGA 泛函。我们将由此产生的 XDM 校正泛函应用于四个卤键晶体：Cl、Br、I 和 ICl。GGA 泛函严重高估了它们的晶格能，而杂化泛函给出了准确的值。GGA 泛函对 Br 和 Cl 晶体中单原子结构的偏好也得到了解释。最后，我们应用最近开发的方法来计算 Bader 的离域指数，以研究卤化物分子晶体中分子间离域的程度。结果表明，分子间离域指数可用于测量晶体中卤键的强度，并检测离域误差的存在。
