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Abstract：
Dynamical refinement is a well established method for refining crystal structures against 3D electron diffraction (ED) data and its benefits have been discussed in the literature [Palatinus, Petříček & Corrêa, (2015). Acta Cryst. A71, 235-244; Palatinus, Corrêa et al. (2015). Acta Cryst. B71, 740-751]. However, until now, dynamical refinements have only been conducted using the independent atom model (IAM). Recent research has shown that a more accurate description can be achieved by applying the transferable aspherical atom model (TAAM), but this has been limited only to kinematical refinements [Gruza et al. (2020). Acta Cryst. A76, 92-109; Jha et al. (2021). J. Appl. Cryst. 54, 1234-1243]. In this study, we combine dynamical refinement with TAAM for the crystal structure of 1-methyluracil, using data from precession ED. Our results show that this approach improves the residual Fourier electrostatic potential and refinement figures of merit. Furthermore, it leads to systematic changes in the atomic displacement parameters of all atoms and the positions of hydrogen atoms. We found that the refinement results are sensitive to the parameters used in the TAAM modelling process. Though our results show that TAAM offers superior performance compared with IAM in all cases, they also show that TAAM parameters obtained by periodic DFT calculations on the refined structure are superior to the TAAM parameters from the UBDB/MATTS database. It appears that multipolar parameters transferred from the database may not be sufficiently accurate to provide a satisfactory description of all details of the electrostatic potential probed by the 3D ED experiment.
摘要：
动态细化是一种针对3D电子衍射（ED）数据细化晶体结构的成熟方法，文献[Palatinus，佩特西克&科列塔,(2015)。ActaCryst.A71,235-244;Palatinus,Corráaetal.(2015)。ActaCryst.B71,740-751].然而,直到现在,动力学细化仅使用独立原子模型(IAM)进行。最近的研究表明，通过应用可转移的非球形原子模型（TAAM）可以实现更准确的描述，但这仅限于运动学上的改进[Gruza等人。（2020年）。ActaCryst.A76,92-109;Jha等人。（2021年）。J.应用。Cryst.54,1234-1243]。在这项研究中,我们将1-甲基尿嘧啶的晶体结构与TAAM结合起来，使用来自进动ED的数据。我们的结果表明，这种方法改善了剩余的傅立叶静电势和完善的品质因数。此外，它导致所有原子的原子位移参数和氢原子的位置发生系统变化。我们发现，细化结果对TAAM建模过程中使用的参数敏感。尽管我们的结果表明，在所有情况下，TAAM与IAM相比都具有卓越的性能，它们还表明，通过对细化结构进行周期性DFT计算获得的TAAM参数优于UBDB/MATTS数据库中的TAAM参数。看来，从数据库传输的多极参数可能不够准确，无法对3DED实验探测的静电势的所有细节提供令人满意的描述。
