Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, 101 Żwirki i Wigury, 02-089 Warszawa, Poland.
College of Inter-Faculty Individual Studies in Mathematics and Natural Sciences (MISMaP), University of Warsaw, 2C Stefana Banacha, 02-097 Warszawa, Poland.
Molecules. 2021 Jun 18;26(12):3730. doi: 10.3390/molecules26123730.
Quantum crystallography is a fast-developing multidisciplinary area of crystallography. In this work, we analyse the influence of different charge density models (i.e., the multipole model (MM), Hirshfeld atom refinement (HAR), and the transferable aspherical atom model (TAAM)), modelling of the thermal motion of hydrogen atoms (anisotropic, isotropic, and with the aid of SHADE or NoMoRe), and the type of radiation used (Mo Kα and Cu Kα) on the final results. To achieve this aim, we performed a series of refinements against X-ray diffraction data for three model compounds and compared their final structures, geometries, shapes of ADPs, and charge density distributions. Our results were also supported by theoretical calculations that enabled comparisons of the lattice energies of these structures. It appears that geometrical parameters are better described (closer to the neutron values) when HAR is used; however, bonds to H atoms more closely match neutron values after MM or TAAM refinement. Our analysis shows the superiority of the NoMoRe method in the description of H-atom ADPs. Moreover, the shapes of the ADPs of H atoms, as well as their electron density distributions, were better described with low-resolution Cu Kα data in comparison to low-resolution Mo Kα data.
量子晶体学是晶体学中一个快速发展的多学科领域。在这项工作中，我们分析了不同电荷密度模型（即多极矩模型（MM）、Hirshfeld 原子精修（HAR）和可转移非球原子模型（TAAM））、氢原子热运动模型（各向异性、各向同性和使用 SHADE 或 NoMoRe）以及使用的辐射类型（Mo Kα 和 Cu Kα）对最终结果的影响。为了实现这一目标，我们对三种模型化合物的 X 射线衍射数据进行了一系列精修，并比较了它们的最终结构、几何形状、各向异性参数形状和电荷密度分布。我们的结果还得到了理论计算的支持，这些计算使这些结构的晶格能得以比较。结果表明，当使用 HAR 时，几何参数描述得更好（更接近中子值）；然而，在 MM 或 TAAM 精修后，与 H 原子的键更接近中子值。我们的分析表明，在描述 H 原子各向异性参数时，NoMoRe 方法具有优越性。此外，与低分辨率 Mo Kα 数据相比，低分辨率 Cu Kα 数据可以更好地描述 H 原子的各向异性参数形状及其电子密度分布。
