Author: Edith Alig

Phase transition of tetragonal copper sulfide Cu2S at low temperatures

The low-temperature behavior of tetragonal copper sulfide, ${\mathrm{Cu}}_{2}\mathrm{S}$, was investigated by powder and single-crystal x-ray diffraction, calorimetry, electrical resistance measurements, and ambient temperature optical absorption spectroscopy. The experiments were complemented by density-functional-theory-based calculations. High-quality, polycrystalline samples and single crystals of tetragonal copper sulfide were synthesized at 5 GPa and 700 K in a large volume multianvil press. Tetragonal ${\mathrm{Cu}}_{2}\mathrm{S}$ undergoes a temperature-induced phase transition to an orthorhombic structure at around 202 K with a hysteresis of $\ifmmode\pm\else\textpm\fi{}21$ K, an e…

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Fast-ADT: A fast and automated electron diffraction tomography setup for structure determination and refinement.

Abstract Electron crystallography has focused in the last few years on the analyses of microcrystals, mainly organic compounds, triggered by recent publications on acquisition methods based on direct detection cameras and continuous stage tilting. However, the main capability of a transmission electron microscope is the access to features at the nanometre scale. In this context, a new acquisition method, called fast and automated diffraction tomography (Fast-ADT), has been developed in form of a general application in order to get the most of the diffraction space from a TEM. It consists of two subsequent tilt scans of the goniometric stage; one to obtain a crystal tracking file and a secon…

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Electron diffraction, X-ray powder diffraction and pair-distribution-function analyses to determine the crystal structures of Pigment Yellow 213, C23H21N5O9.

The crystal structure of the nanocrystalline alpha phase of Pigment Yellow 213 (P.Y. 213) was solved by a combination of single-crystal electron diffraction and X-ray powder diffraction, despite the poor crystallinity of the material. The molecules form an efficient dense packing, which explains the observed insolubility and weather fastness of the pigment. The pair-distribution function (PDF) of the alpha phase is consistent with the determined crystal structure. The beta phase of P.Y. 213 shows even lower crystal quality, so extracting any structural information directly from the diffraction data is not possible. PDF analysis indicates the beta phase to have a columnar structure with a si…

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Electron diffraction tomography and X-ray powder diffraction on photoredox catalyst PDI

N,N-Bis(2,6-diisopropylphenyl)-perylene-3,4,9,10-bis(dicarboximide) (PDI-iPr) is starting to be widely used as a metal-free homogeneous photoredox catalyst. The crystal structure was determined by a combination of electron diffraction tomography and X-ray powder diffraction and further validated by DFT-D calculations. Surprisingly, the molecular geometry of PDI-iPr leads to voids in the packing.

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Crystal Structures and Polymorphism of Nickel and Copper Coordination Polymers with Pyridine Ligands

The crystal structures of a series of pyridine coordination polymers [MIICl2(C5H5N)x]n (M = Ni, Cu), prepared via thermal decomposition are reported. [NiCl2(C5H5N)4] (1) decomposes stepwise via [NiCl2(C5H5N)2]n (2), [NiCl2(C5H5N)]n (3), and [NiCl2(C5H5N)2/3]n (4), to NiCl2 with increasing temperature. The thermal decomposition of [CuCl2(C5H5N)2]n (5), progresses via two polymorphs of [CuCl2(C5H5N)]n (6a and 6b), and [CuCl2(C5H5N)2/3]n (7), to CuCl2. The compounds 3, 4, and 7 were prepared as pure phases. All crystal structures were determined by X-ray powder diffraction. Notably, the crystal structures of the polymorphs 6a and 6b were determined from powder diffraction data of a mixture of …

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