International Union of CrystallographyActa Medica Okayama2052-2525732020Strong hydrogen bonding in a dense hydrous magnesium silicate discovered by neutron Laue diffraction370374ENNarangooPurevjavInstitute for Planetary Materials, Okayama UniversityTakuoOkuchiInstitute for Planetary Materials, Okayama UniversityChristinaHoffmanNeutron Scattering Division, Neutron Sciences Directorate, Oak Ridge National LaboratoryA large amount of hydrogen circulates inside the Earth, which affects the long-term evolution of the planet. The majority of this hydrogen is stored in deep Earth within the crystal structures of dense minerals that are thermodynamically stable at high pressures and temperatures. To understand the reason for their stability under such extreme conditions, the chemical bonding geometry and cation exchange mechanism for including hydrogen were analyzed in a representative structure of such minerals (i.e. phase E of dense hydrous magnesium silicate) by using time-of-flight single-crystal neutron Laue diffraction. Phase E has a layered structure belonging to the space group R (3) over barm and a very large hydrogen capacity (up to 18% H2O weight fraction). It is stable at pressures of 13-18 GPa and temperatures of up to at least 1573 K. Deuterated high-quality crystals with the chemical formula Mg2.28Si1.32D2.15O6 were synthesized under the relevant high-pressure and high-temperature conditions. The nuclear density distribution obtained by neutron diffraction indicated that the O-D dipoles were directed towards neighboring O2- ions to form strong interlayer hydrogen bonds. This bonding plays a crucial role in stabilizing hydrogen within the mineral structure under such high-pressure and high-temperature conditions. It is considered that cation exchange occurs among Mg2+, D+ and Si4+ within this structure, making the hydrogen capacity flexible.No potential conflict of interest relevant to this article was reported.International Union of CrystallographyActa Medica Okayama0909-04951862011Development of a soft X-ray angle-resolved photoemission system applicable to 100 µm crystals879884ENTakayukiMuroyukakoKatoTomohiroMatsushitaToyohikoKinoshitaYoshioWatanabeHiroyukiOkazakiTakayoshiYokoyaAkiraSekiyamahigemasaSugaA system for angle-resolved photoemission spectroscopy (ARPES) of small single crystals with sizes down to 100 µm has been developed. Soft X-ray synchrotron radiation with a spot size of `40 µm ~ 65 µm at the sample position is used for the excitation. Using this system an ARPES measurement has been performed on a Si crystal of size 120 µm ~ 100 µm ~ 80 µm. The crystal was properly oriented on a sample stage by measuring the Laue spots. The crystal was cleaved in situ with a microcleaver at 100 K. The cleaved surface was adjusted to the beam spot using an optical microscope. Consequently, clear band dispersions along the Γ-X direction reflecting the bulk electronic states were observed with a photon energy of 879 eV.No potential conflict of interest relevant to this article was reported.International Union of CrystallographyActa Medica Okayama2056-989076112020Crystal structures of four isomeric hydrogen-bonded co-crystals of 6-methylquinoline with 2-chloro-4-nitrobenzoic acid, 2-chloro-5-nitrobenzoic acid, 3-chloro-2-nitrobenzoic acid and 4-chloro-2-nitrobenzoic acid17011707ENKazumaGotohDepartment of Chemistry, Faculty of Science, Okayama UniversityHiroyukiIshidaDepartment of Chemistry, Faculty of Science, Okayama UniversityThe structures of the four isomeric compounds of 6-methylquinoline with chloro- and nitro-substituted benzoic acids, C7H4ClNO4·C10H9N, namely, 2-chloro-4-nitrobenzoic acid–6-methylquinoline (1/1), (I), 2-chloro-5-nitrobenzoic acid–6-methylquinoline (1/1), (II), 3-chloro-2-nitrobenzoic acid–6-methylquinoline (1/1), (III), and 4-chloro-2-nitrobenzoic acid–6-methylquinoline (1/1), (IV), have been determined at 185–190 K. In each compound, the acid and base molecules are linked by a short hydrogen bond between a carboxyl O atom and an N atom of the base. The O⋯N distances are 2.5452 (12), 2.6569 (13), 2.5640 (17) and 2.514 (2) Å, respectively, for compounds (I)–(IV). In the hydrogen-bonded acid–base units of (I), (III) and (IV), the H atoms are each disordered over two positions with O site:N site occupancies of 0.65 (3):0.35 (3), 0.59 (4):0.41 (4) and 0.48 (5):0.52 (5), respectively, for (I), (III) and (IV). The H atom in the hydrogen-bonded unit of (II) is located at the O-atom site. In all of the crystals of (I)–(IV), – interactions between the quinoline ring system and the benzene ring of the acid molecule are observed. In addition, a – interaction between the benzene rings of adjacent acid molecules and a C\H⋯O hydrogen bond are observed in the crystal of (I), and C\H⋯O hydrogen bonds and O⋯Cl contacts occur in the crystals of (III) and (IV). These intermolecular interactions connect the acid and base molecules, forming a layer structure parallel to the bc plane in (I), a column along the a-axis direction in (II), a layer parallel to the ab plane in (III) and a three-dimensional network in (IV). Hirshfeld surfaces for the title compounds mapped over dnorm and shape index were generated to visualize the weak intermolecular interactions.No potential conflict of interest relevant to this article was reported.International Union of CrystallographyActa Medica Okayama2056-9890752019Crystal structure of 4-chloro-2-nitrobenzoic acid with 4-hydroxyquinoline: a disordered structure over two states of 4-chloro-2-nitrobenzoic acid-quinolin-4(1H)-one (1/1) and 4-hydroxyquinolinium 4-chloro-2-nitrobenzoate1853ENKazumaGotohDepartment of Chemistry, Faculty of Science, Okayama UniversityHiroyukiIshidaDepartment of Chemistry, Faculty of Science, Okayama UniversityThe title compound, C9H7.5NO center dot C7H3.5ClNO4, was analysed as a disordered structure over two states, viz. co-crystal and salt, accompanied by a keto-enol tautomerization in the base molecule. The co-crystal is 4-chloro-2-nitrobenzoic acid-quinolin-4(1H)-one (1/1), C7H4ClNO4 center dot C9H7NO, and the salt is 4-hydroxy-quinolinium 4-chloro-2-nitrobenzoate, C9H8NO+center dot C7H3ClNO4. In the compound, the acid and base molecules are held together by a short hydrogen bond [O center dot center dot center dot O = 2.4393 (15) angstrom], in which the H atom is disordered over two positions with equal occupancies. In the crystal, the hydrogen-bonded acid-base units are linked by N-H center dot center dot center dot O and C-H center dot center dot center dot O hydrogen bonds, forming a tape structure along the a-axis direction. The tapes are stacked into a layer parallel to the ab plane via pi-pi interactions [centroid-centroid distances = 3.5504 (8)-3.9010 (11) angstrom]. The layers are further linked by another C-H center dot center dot center dot O hydrogen bond, forming a three-dimensional network. Hirshfeld surfaces for the title compound mapped over shape-index and d orm were generated to visualize the intermolecular interactions.No potential conflict of interest relevant to this article was reported.International Union of CrystallographyActa Medica Okayama0909-04952812021Absolute X-ray energy measurement using a high-accuracy angle encoder111119ENTakahikoMasudaResearch Institute for Interdisciplinary Science, Okayama UniversityTsukasaWatanabeNational Institute of Advanced Industrial Science and TechnologyKjeldBeeksInstitute for Atomic and Subatomic Physics – AtominstitutHiroyukiFujimotoNational Institute of Advanced Industrial Science and TechnologyTakahiroHirakiResearch Institute for Interdisciplinary Science, Okayama UniversityHiroyukiKainoResearch Institute for Interdisciplinary Science, Okayama UniversityShinjiKitaoNational Institute of Advanced Industrial Science and TechnologyYukiMiyamotoResearch Institute for Interdisciplinary Science, Okayama UniversityKoichiOkaiResearch Institute for Interdisciplinary Science, Okayama UniversityNoboruSasaoResearch Institute for Interdisciplinary Science, Okayama UniversityMakotoSetoInstitute for Integrated Radiation and Nuclear Science, Kyoto UniversityThorstenSchummInstitute for Atomic and Subatomic Physics – AtominstitutYudaiShigekawaRIKENKenjiTamasakuRIKEN, SPring-8 CenterSatoshiUetakeResearch Institute for Interdisciplinary Science, Okayama UniversityAtsushiYamaguchiRIKENYoshitakaYodaJapan Synchrotron Radiation Research InstituteAkihiroYoshimiResearch Institute for Interdisciplinary Science, Okayama UniversityKojiYoshimuraResearch Institute for Interdisciplinary Science, Okayama UniversityThis paper presents an absolute X-ray photon energy measurement method that uses a Bond diffractometer. The proposed system enables the prompt and rapid in situ measurement of photon energies over a wide energy range. The diffractometer uses a reference silicon single-crystal plate and a highly accurate angle encoder called SelfA. The performance of the system is evaluated by repeatedly measuring the energy of the first excited state of the potassium-40 nuclide. The excitation energy is determined as 29829.39 (6) eV, and this is one order of magnitude more accurate than the previous measurement. The estimated uncertainty of the photon energy measurement was 0.7 p.p.m. as a standard deviation and the maximum observed deviation was 2 p.p.m.No potential conflict of interest relevant to this article was reported.