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The high‐precision X‐ray diffraction setup for work with diamond anvil cells (DACs) in interaction chamber 2 (IC2) of the High Energy Density instrument of the European X‐ray Free‐Electron Laser is described. This includes beamline optics, sample positioning and detector systems located in the multipurpose vacuum chamber. Concepts for pump–probe X‐ray diffraction experiments in the DAC are described and their implementation demonstrated during the First User Community Assisted Commissioning experiment. X‐ray heating and diffraction of Bi under pressure, obtained using 20 fs X‐ray pulses at 17.8 keV and 2.2 MHz repetition, is illustrated through splitting of diffraction peaks, and interpreted employing finite element modeling of the sample chamber in the DAC. [ABSTRACT FROM AUTHOR]

Crystallization of the Ph3Sb(O2CCH2−CH=CH2)2 complex upon fast solvent (benzene) evaporation gives monoclinic crystals (I), whereas in the case of slow evaporation, triclinic crystals are formed (II). Also, monoclinic crystals are spontaneously transformed into triclinic crystals within 6 months. It was shown that the presence of voids near one carboxylate ligand in the monoclinic phase of Ph3Sb-(O2CCH2−CH=CH2)2 decreases the energy of intermolecular interactions and, as a consequence, leads to a conformational transition with a noticeable decrease in the crystal lattice energy. Thus, the presence of voids in the monoclinic phase crystal allows the formation of a thermodynamically more favorable conformation of the molecule in the crystal. Several structural models were determined for the Ph3Sb(O2CCH2−CH=CH2)2 complex (CIF files no. 1887561 (IIAM), model of non-interacting atoms; 1887562 (I), multipole model; 1887563 (IIIAM), model of non-interacting atoms; 1887564 (II), multipole model). [ABSTRACT FROM AUTHOR]

Abstract: The electron density distribution in Ph3Sb(O2CC(Me)=CH2)2 ⋅ C6H6 and structural and energy aspects of the phase transition in the crystals of this compound were investigated using a series of common (Ib−Ie) and high-precision (Ia) X-ray diffraction experiments. A considerable difference between the root-mean-square atomic displacements in two chemically equivalent methyl groups of the methacrylate ligands was revealed. This difference was shown to be caused by considerable energy difference of the intra- and intermolecular contacts of the corresponding methyl groups. [ABSTRACT FROM AUTHOR]

The crystal structure of MoS was for the first time refined based on precise three-dimensional X-ray diffraction data collected from the synthesized single crystal. The results of the refinement using the Hansen-Coppens multipole model based on X-ray diffraction data and quantum chemical calculations for the molybdenum disulfide monolayer and single crystal were analyzed in terms of Bader's quantum theory of Atoms in Molecules (QTAIM). An analysis of the bond critical points (bcp) for S...S attests to a weak van der Waals interaction having the energy of ∼1.25 kcal mol per S...S contact and the binding energy of the layers of ∼7.5 kcal mol. [ABSTRACT FROM AUTHOR]