Berzelii Center EXSELENT on Porous Materials and Inorganic and Structural Chemistry, Department of Materials and Environmental Chemistry, Stockholm University, SE-10691 Stockholm, Sweden.
IUCrJ. 2015 Feb 10;2(Pt 2):267-82. doi: 10.1107/S2052252514028188. eCollection 2015 Mar 1.
Phase identification and structure determination are important and widely used techniques in chemistry, physics and materials science. Recently, two methods for automated three-dimensional electron diffraction (ED) data collection, namely automated diffraction tomography (ADT) and rotation electron diffraction (RED), have been developed. Compared with X-ray diffraction (XRD) and two-dimensional zonal ED, three-dimensional ED methods have many advantages in identifying phases and determining unknown structures. Almost complete three-dimensional ED data can be collected using the ADT and RED methods. Since each ED pattern is usually measured off the zone axes by three-dimensional ED methods, dynamic effects are much reduced compared with zonal ED patterns. Data collection is easy and fast, and can start at any arbitrary orientation of the crystal, which facilitates automation. Three-dimensional ED is a powerful technique for structure identification and structure solution from individual nano- or micron-sized particles, while powder X-ray diffraction (PXRD) provides information from all phases present in a sample. ED suffers from dynamic scattering, while PXRD data are kinematic. Three-dimensional ED methods and PXRD are complementary and their combinations are promising for studying multiphase samples and complicated crystal structures. Here, two three-dimensional ED methods, ADT and RED, are described. Examples are given of combinations of three-dimensional ED methods and PXRD for phase identification and structure determination over a large number of different materials, from Ni-Se-O-Cl crystals, zeolites, germanates, metal-organic frameworks and organic compounds to intermetallics with modulated structures. It is shown that three-dimensional ED is now as feasible as X-ray diffraction for phase identification and structure solution, but still needs further development in order to be as accurate as X-ray diffraction. It is expected that three-dimensional ED methods will become crucially important in the near future.
相鉴定和结构测定是化学、物理和材料科学中重要且广泛应用的技术。最近，已经开发出了两种用于自动化三维电子衍射（ED）数据采集的方法，即自动衍射层析（ADT）和旋转电子衍射（RED）。与 X 射线衍射（XRD）和二维带状 ED 相比，三维 ED 方法在鉴定相和确定未知结构方面具有许多优势。使用 ADT 和 RED 方法几乎可以完全采集三维 ED 数据。由于每个 ED 图案通常是通过三维 ED 方法偏离晶带轴进行测量的，因此与带状 ED 图案相比，动态效应大大降低。数据采集既简单又快速，并且可以从晶体的任意取向开始，这便于自动化。三维 ED 是从单个纳米或微米大小的颗粒中鉴定结构和解决结构的强大技术，而粉末 X 射线衍射（PXRD）则提供了样品中存在的所有相的信息。ED 受到动态散射的影响，而 PXRD 数据是运动学的。三维 ED 方法和 PXRD 是互补的，它们的组合有望用于研究多相样品和复杂晶体结构。在这里，描述了两种三维 ED 方法，ADT 和 RED。给出了大量不同材料的三维 ED 方法与 PXRD 组合的示例，这些材料包括 Ni-Se-O-Cl 晶体、沸石、锗酸盐、金属有机骨架和有机化合物，以及具有调制结构的金属间化合物。结果表明，三维 ED 现在与 X 射线衍射一样可行，可用于相鉴定和结构解析，但仍需要进一步发展，才能达到与 X 射线衍射一样准确。预计在不久的将来，三维 ED 方法将变得至关重要。
