A specialized quantum area detector for electron diffraction studies makes it possible to solve the structure of small organic compound nanocrystals in non-cryo conditions by direct methods.

In this work a new ultrafast data collection strategy for electron diffraction tomography is presented that allows reducing data acquisition time by one order of magnitude. This methodology minimizes the radiation damage of beam-sensitive materials, such as microporous materials. This method, combined with the precession of the electron beam, provides high quality data enabling the determination of very complex structures. Most importantly, the implementation of this new electron diffraction methodology is easily affordable in any modern electron microscope. As a proof of concept, we have solved a new highly complex zeolitic structure named ITQ-58, with a very low symmetry (triclinic) and a large unit cell volume (1874.6 Å3), containing 16 silicon and 32 oxygen atoms in its asymmetric unit, which would be very difficult to solve with the state of the art techniques.

The crystal structures of two important marketed pharmaceuticals, namely, ramelteon (RAM) and tolvaptan (TOL), were determined for the first time using 3D precession electron diffraction tomography (PEDT) on 500 nm-sized crystals. The results were compared with the same structures determined by single-crystal X-ray diffraction on subsequently grown 50−200 μm single crystals, indicating a good match of molecular conformation, crystal packing, and unit cell parameters. The X-ray crystal structures were used to validate the developed workflow of data acquisition and structure solution with electron diffraction. This study highlights that 3D PEDT alone is able to provide accurate crystal structures from pharmaceutical nanocrystals that will suffice for most practical applications when no larger crystals can be grown.

Atomic pair distribution function (PDF) analysis has been widely used to investigate nanocrystalline and structurally disordered materials. Experimental PDFs retrieved from electron diffraction (ePDF) in transmission electron microscopy (TEM) represent an attractive alternative to traditional PDF obtained from synchrotron X-ray sources, particularly for studying minute samples. Nonetheless, the inelastic scattering produced by the large dynamical effects of electron diffraction may obscure the interpretation of ePDF. In the present work, precession electron diffraction (PED-TEM) has been employed to obtain the ePDF of two different sampleslipoic acid-and hexanethiolate-capped gold nanoparticles (∼4.5 and 4.2 nm, respectively)randomly oriented and measured at both liquid nitrogen and room temperatures. The electron diffraction data were processed to obtain ePDFs which were subsequently compared with the PDF of different ideal structure models. The results demonstrate that the PED-ePDF data are sensitive to different crystalline structures such as monocrystalline (truncated octahedra) and multiply twinned (decahedra, icosahedra) structures. The results indicate that PED reduces the residual from 46 to 29%; in addition, the combination of PED and low temperature further reduced the residual to 23%, which is comparable to X-ray PDF analysis. Furthermore, the inclusion of PED resulted in a better estimation of the coordination number from ePDF. To the best of our knowledge, the precessed electron-beam technique (PED) has not been previously applied to nanoparticles for analysis by the ePDF method.

A correction is made to the article by van Genderen et al. [Acta Cryst. (2016), A72, 236–242].