Radiation sensitive materials are among the most difficult materials to study, even more so if they exist only as nanometer-sized particles, where their size is either intentional because of enhanced properties at the nano-scale or it is unintentional because it is impossible to obtain bigger particles of the same structure. In both cases characterization methods need to be optimized to get the most information out of these particles before the radiation damages them to a point where their structure is altered. When the particles are crystallized, both characteristics, the small size and the beam sensitivity, call for electron diffraction as a privileged investigation tool. The strong interaction of electrons (as compared to X-rays) with matter allows single crystal diffraction experiments on nanometer-sized crystals and for the same amount of beam damage, electron diffraction yields more information than X-rays. These inherent advantages of electron diffraction are optimized in the recently developed low-dose electron diffraction tomography (LD-EDT) by minimizing the necessary dose for a complete data collection. In this contribution we show that in some cases even doses as low as 2 e/Ų can induce damage in crystal structures that inhibit a correct structure refinement. However, by LD-EDT we can obtain data using extremely low doses that don’t alter the structure which make it then possible not only to solve crystal structures but also to refine them using dynamical diffraction theory. Here a synthetic oxide containing volatile Na and a metal-organic framework are given as examples. A dynamical refinement of the structures is possible with data sets requiring a dose of less than 0.15 e/Ų.

中文翻译：

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光束敏感纳米晶体的结构解析和细化

辐射敏感材料是最难研究的材料之一，如果它们仅以纳米尺寸的颗粒存在，则更是如此，它们的尺寸要么是有意的，因为纳米尺度的性能增强，要么是无意的，因为不可能获得相同结构的较大颗粒。在这两种情况下，都需要优化表征方法，以便在辐射将粒子损坏到结构发生改变之前从这些粒子中获取最多信息。当粒子结晶时，小尺寸和光束敏感性这两个特征都需要电子衍射作为一种特殊的研究工具。电子（与 X 射线相比）与物质的强烈相互作用允许在纳米尺寸的晶体上进行单晶衍射实验，并且对于相同量的束损伤，电子衍射比 X 射线产生更多的信息。电子衍射的这些固有优势在最近开发的低剂量电子衍射断层扫描 (LD-EDT) 中得到了优化，通过最大限度地减少完整数据收集所需的剂量。在这篇文章中，我们表明，在某些情况下，即使剂量低至 2 e/Ų，也会引起晶体结构损伤，从而抑制正确的结构细化。然而，通过 LD-EDT，我们可以使用极低的剂量获得数据，而不会改变结构，这使得不仅可以求解晶体结构，还可以使用动态衍射理论对其进行细化。这里给出了含有挥发性Na和金属有机骨架的合成氧化物作为例子。使用剂量低于 0.15 e/Ų 的数据集可以对结构进行动态细化。