The lithium‐conducting, rare‐earth halides, Li₃MX₆ (M = Y, Er; X = Cl, Br), have garnered significantly rising interest recently, as they have been reported to have oxidative stability and high ionic conductivities. However, while a multitude of materials exhibit a superionic conductivity close to 1 mS cm⁻¹, the exact design strategies to further improve the ionic transport properties have not been established yet. Here, the influence of the employed synthesis method of mechanochemical milling, compared to subsequent crystallization routines as well as classic solid‐state syntheses on the structure and resulting transport behavior of Li₃ErCl₆ and Li₃YCl₆ are explored. Using a combination of X‐ray diffraction, pair distribution function analysis, density functional theory, and impedance spectroscopy, insights into the average and local structural features that influence the underlying transport are provided. The existence of a cation defect within the structure in which Er/Y are disordered to a new position strongly benefits the transport properties. A synthetically tuned, increasing degree of this disordering leads to a decreasing activation energy and increasing ionic conductivity. This work sheds light on the possible synthesis strategies and helps to systematically understand and further improve the properties of this class of materials.

Structured solvents near nanoparticles: The physical properties and reactivity of nanoparticles in solution depend not only on their surface termination but also on changes in solvent ordering caused by the presence of the interface created by the nanoparticle. Zobel et al. used x-ray scattering to study solvent ordering for a variety of metal and metal-oxide nanoparticles in a variety of polar solvents (alcohols) and a nonpolar solvent (n-hexane). They observed layers of enhanced ordering near the nanoparticle surface relative to the bulk solvent. These trends were largely independent of surface chemistry, such as changing the surface groups from hydroxyls to carboxylates. Science , this issue p. 292

Nanoparticles in solution interact with their surroundings via hydration shells. Although the structure of these shells is used to explain nanoscopic properties, experimental structural insight is still missing. Here we show how to access the hydration shell structures around colloidal nanoparticles in scattering experiments. For this, we synthesize variably functionalized magnetic iron oxide nanoparticle dispersions. Irrespective of the capping agent, we identify three distinct interatomic distances within 2.5 Å from the particle surface which belong to dissociatively and molecularly adsorbed water molecules, based on theoretical predictions. A weaker restructured hydration shell extends up to 15 Å. Our results show that the crystal structure dictates the hydration shell structure. Surprisingly, facets of 7 and 15 nm particles behave like planar surfaces. These findings bridge the large gap between spectroscopic studies on hydrogen bond networks and theoretical advances in solvation science.

Over the last decade, some studies with laboratory pair distribution function (PDF) data emerged. Yet, limited Q_max or instrumental resolution impeded in-depth structural refinements. With more advanced detector technologies, the question arose how to design novel PDF equipment for laboratories that will allow decent PDF refinements over r = 1–70 Å. It is crucial to reflect the essential requirements, namely, monochromatic X-rays, suppression of air scattering, instrumental resolution, and overall measurement times. The result is a novel PDF setup based on a STOE STADI P powder diffractometer in transmission-/Debye-Scherrer geometry with monochromatic Ag Kα₁ radiation, featuring a MYTHEN2 4K detector covering a Q range of 0.3–20.5 Å⁻¹. PDF data are collected in a moving PDF mode within 6 h. Structural signatures of liquids can be satisfactorily resolved in the PDF as shown for the ionic liquid hmimPF₆. The high instrumental resolution is mirrored in low q_damp values determined from LaB₆ measurements. PDF data from a powder sample of ca. 7 nm TiO₂ nanoparticles were successfully refined over up to 70 Å with goodness-of-fit values R_w < 0.22 (respectively R_w = 0.18 over 30 Å), thanks to the low background and high instrumental resolution, hereby enlarging the accessible r range by several tens of Angstroms compared to previous laboratory PDF studies.