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Acta Cryst. (2014). A70, C1079
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Determination of lattice constants is a crucial process in analyzing powder diffraction data, affecting the robustness of analyses in subsequent steps. A number of algorithms and software based on them to predict lattice constants from powder data have been reported. In this study, we propose a novel experimental approach to facilitate unambiguous determination of the crystal systems and resulting lattice constants from a microcrystalline powder sample. Efforts have been made for partial recovery of crystal anisotropy from a complete random orientation in powder in order to facilitate the analysis of powder data. Our approach makes use of magnetic orientation[1-3] of microcrystals occurring due to the diamagnetic anisotropy inherent to crystal. By application of a static/or rotating magnetic field, the easy/or hard magnetization axes of microcrystals undergo uniaxial alignment, giving rise to two different fiber diffraction patterns. These patterns reflect the crystal symmetry, enabling us to discriminate the crystal system. Crystals of known crystal system were pulverized and their suspensions were prepared. Each suspension was subjected to a static/or rotating magnetic field and the X-ray diffraction measurement was performed in situ to obtain two fiber diffraction patterns. It is evident that isotropic crystals only produce ring patterns for static and rotating measurement. On the other hand, biaxial crystals exhibit sharp diffraction spots in both fiber patterns. Furthermore, these fiber patterns exhibit layer lines in both patterns for the orthorhombic system, no layer lines for triclinic system, etc. In addition, overlapping of peaks in one-dimensional powder pattern can be resolved by indexing the spots in two dimensions of fiber patterns.

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Acta Cryst. (2014). A70, C1136
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A three dimensionally magnetically oriented microcrystal array (3D-MOMA) is attractive to determination of a crystal structure as well as a molecular structure because it does not require a single crystal with sufficient size and quality for diffraction studies. We have developed a novel method to fabricate 3D-MOMA and determined several crystal structures using the 3D-MOMAs[1],[2]. However, the structure determination through MOMA requires a solidification treatment with UV curable monomer prior to X-ray diffraction experiment. We have developed a new X-ray diffractometer equipped with a magnetic field generator, which makes it possible to collect diffraction data without the solidification treatment. In this poster, we describe X-ray diffraction analyses of a magnetically oriented microcrystal suspension (MOMS) of L-alanine without the solidification treatment. A suspension of L-alanine microcrystals was poured in a glass capillary and rotated at a constant speed in a magnetic circuit attached in the X-ray diffractometer. Then, diffraction images were collected every 60 seconds. In the initial phase, the diffraction pattern showed a broad shape similar to that from a powder sample. As time goes on, diffraction patterns have gradually changed to single-crystal like patterns. After 2 hours, the shape of diffraction spots became as sharp as that of a single crystal. This observation shows that the microcrystals are oriented in the same direction. Owing to the improvement of the magnetic circuit and X-ray diffractometer, the quality of the diffraction has been greatly improved compared to that reported previously[3]. Further details of the analyses will be shown in the poster.

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Acta Cryst. (2014). A70, C1139
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We have proposed magnetically oriented microcrystal array (MOMA) technique as a new technique of crystal structure analysis. With this technique, single crystal X-ray diffraction analysis is made possible from a microcrystalline powder. Biaxial crystals, having three different values of magnetic susceptibility (χ1>χ2>χ3), are aligned three dimensionally under a frequency-modulated elliptical magnetic field. Biaxial microcrystal suspended in an ultraviolet (UV) light-curable monomer matrix is aligned three dimensionally under the magnetic field, followed by consolidation of the alignment by the photopolymerization the matrix. Biaxial crystal group has three crystal systems: orthorhombic, monoclinic and triclinic systems. The analysis of crystals belonging to the triclinic system is important because ca. 23 % of organic crystals are triclinic. We have so far succeeded in determining crystal structures of orthorhombic and monoclinic systems by using the MOMA technique[1, 2, 3] but crystals of triclinic system have not been examined yet. Therefore, in this report, we attempt to determine the crystal structure of D-arabinitol, belonging to the triclinic system, by using the MOMA technique. 10 wt% D-arabinitol / XVL14 (UV light-curable monomer) suspension was subjected to 8-T magnetic field (the speed of rotation changed between 10 rpm and 40 rpm at every 900) and was consolidated by irradiation of UV light. The prepared MOMA was subjected to the X-ray diffraction measurement. The obtained diffraction spots were well resolved and the average of half widths was about 3.90. These results indicate that the D-arabinitol microcrystals were aligned three dimensionally in the MOMA and the high quality of alignment was achieved. These results indicate that the obtained diffraction patterns are equivalent to those obtained from corresponding single crystal.
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