The advancement in 3D electron diffraction (3D ED) techniques that lead to a revolution in molecular structure determination using nano-sized crystals is now achieving atomic resolution. The structures can be obtained from 3D ED data with tools similar to those used for X-ray structure determination. In this context, the MoPro software, originally designed for structure and charge density refinements using X-ray diffraction data, has been adapted. Structure refinement on 3D ED data was achieved via implementation of electron scattering factors available in the literature and by application of the Mott–Bethe equation to X-ray scattering factors computed from the multipolar atom model. The multipolar model was parametrized using the transferable pseudoatom databanks ELMAM2 and UBDB. Applying the independent atom model (IAM), i.e. spherical neutral atom refinement, to 3D ED data on β-glycine in MoPro resulted in structure and refinement statistics comparable to those obtained from other well known software. Use of the transferred aspherical atom model (TAAM) led to improvement of the refinement statistics and a better fit of the model to the 3D ED data as compared with the spherical atom refinement. The anisotropic displacement parameters of non-H atoms appear underestimated by typically 0.003 Ų for the non-H atoms in IAM refinement compared with TAAM. Thus, MoPro is shown to be an effective tool for crystal structure refinement on 3D ED data and allows use of a spherical or a multipolar atom model. Electron density databases can be readily transferred with no further modification needed when the Mott–Bethe equation is applied.

中文翻译：

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改进 MoPro 中 β-甘氨酸的电子衍射数据：寻求改进的结构模型

3D 电子衍射 (3D ED) 技术的进步导致了使用纳米尺寸晶体确定分子结构的革命，现在正在实现原子分辨率。可以使用类似于用于 X 射线结构确定的工具从 3D ED 数据中获得结构。在此背景下，MoPro最初设计用于使用 X 射线衍射数据进行结构和电荷密度细化的软件已经过调整。3D ED 数据的结构改进是通过实现文献中可用的电子散射因子以及将 Mott-Bethe 方程应用于从多极原子模型计算的 X 射线散射因子来实现的。使用可转移的伪原子数据库 ELMAM2 和 UBDB 对多极模型进行参数化。将独立原子模型 (IAM)，即球形中性原子细化应用于MoPro 中β-甘氨酸的 3D ED 数据导致结构和细化统计数据与从其他知名软件获得的数据相当。与球形原子细化相比，使用转移的非球面原子模型 (TAAM) 导致了细化统计的改进和模型对 3D ED 数据的更好拟合。与 TAAM 相比，IAM 精修中的非 H 原子的非 H 原子的各向异性位移参数通常被低估了 0.003 Å ²。因此，MoPro被证明是对 3D ED 数据进行晶体结构细化的有效工具，并允许使用球形或多极原子模型。当应用 Mott-Bethe 方程时，无需进一步修改即可轻松传输电子密度数据库。