Pushing data quality for laboratory pair distribution function experiments

Abstract

Over the last decade, some studies with laboratory pair distribution function (PDF) data emerged. Yet, limited Qmax 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 qdamp 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 Rw < 0.22 (respectively Rw = 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.

Mechanochemical Synthesis: A Tool to Tune Cation Site Disorder and Ionic Transport Properties of Li3MCl6 (M = Y, Er) Superionic Conductors

“…For more information on this dedicated diffractometer for pair distribution function analyses, please see ref. . All samples were sealed in glass capillaries (Ø = 0.5 mm) prior to measurement collection, which was carried out in the Q ‐range of 0.3–20.5 Å −1 .…”

“…In case of all crystalline samples, the fits were carried out using PDFGui . The instrumental resolution parameter q damp (0.011) and q broad (0.010) corresponding to the used instrument are known from a LaB 6 standard . After accounting for the background and sample absorption, the initial refinement included: 1) the scale factor and the atomic correlated motion factor, followed by 2) the lattice parameters.…”

Hard X-ray-based techniques for structural investigations of CO2 methanation catalysts prepared by MOF decomposition

“…For more information on this dedicated diffractometer for pair distribution function analysis, see ref. 41. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was performed with an iCAP 6500 Duo from Thermo Scientific via a six-point calibration.…”

Long‐Term Colloidally Stable Aqueous Dispersions of ≤5 nm Spinel Ferrite Nanoparticles

“…For more information on this dedicated diffractometer for pair distribution function analysis, see. [35] PDF processing was carried out with xPDFsuite [36] using a Q max of 13.0 to 17.5 Å À 1 , and fitting was done with diffpy-CMI. [37] Parameters refined were the scale, cell parameters, crystallite size, correlated atomic motion, atomic position of oxygen, occupancy of octahedral sites and thermal parameters.…”