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Yamashita, Keishiro*; Komatsu, Kazuki*; Hattori, Takanori; Machida, Shinichi*; Kagi, Hiroyuki*
Acta Crystallographica Section B; Structural Science, Crystal Engineering and Materials (Internet), 80(6), p.695 - 705, 2024/12
Times Cited Count：0 Percentile：0.00(Chemistry, Multidisciplinary)So far, the odd hydration number has been missing in the water-rich magnesium chloride hydrate series (MgCl
HO). In this study, we have identified magnesium chloride heptahydrate, MgCl7HO (or MgCl7DO) which forms at high pressures and high temperatures of above 2 GPa and above 300 K, respectively. Its structure has been determined by a combination of 
single crystal X-ray diffraction at 2.5 GPa and 298 K and powder neutron diffraction at 3.1 GPa and 300 K. The results showed an orientational disorder of water molecules, which was also examined by the density-functional-theory calculations. The disorder involves the reconnection of hydrogen bonds, which differs from those in water ice phases and known disordered salt hydrates. The shrinkage by compression occurs mainly in one direction. In the plane perpendicular to this most compressible direction, oxygen and chlorine atoms are in a hexagonal-like arrangement.
Yamashita, Keishiro*; Nakayama, Kazuya*; Komatsu, Kazuki*; Ohara, Takashi; Munakata, Koji*; Hattori, Takanori; Sano, Asami; Kagi, Hiroyuki*
Acta Crystallographica Section B; Structural Science, Crystal Engineering and Materials (Internet), 79(5), p.414 - 426, 2023/10
Times Cited Count：2 Percentile：47.77(Chemistry, Multidisciplinary)The structure of a recently-found hyperhydrated form of sodium chloride, NaCl 13H(D)
O, has been determined by 
single-crystal neutron diffraction at 1.7 GPa and 298 K. It has large hydrogen-bond networks and some water molecules have distorted bonding features such as bifurcated hydrogen bonds and five-coordinated water molecules. The hydrogen-bond network has similarities to ice VI in terms of network topology and disordered hydrogen bonds. Assuming the equivalence of network components connected by pseudo symmetries, the overall network structure of this hydrate can be expressed by breaking it down into smaller structural units which correspond to the ice VI network structure. This hydrogen-bond network contains orientational disorder of water molecules in contrast to the known salt hydrates. Here, we present an example for further insights into a hydrogen-bond network containing ionic species.
'(O'3)-type sodium cobalt oxide Na
CoO (
0.78)Miyazaki, Yuzuru*; Igawa, Naoki; Yubuta, Kunio*
Acta Crystallographica Section B; Structural Science, Crystal Engineering and Materials (Internet), 77(3), p.371 - 377, 2021/06
Times Cited Count：2 Percentile：25.63(Chemistry, Multidisciplinary)Crystal structure of '(O'3)-type layered sodium cobalt oxide NaCoO ( 0.78) was analyzed using the (3+1)-dimensional superspace approach to the neutron diffraction data. The crystal structure is described based on the superspace group 
2 = 
(
0
)00, wherein the positions of Na atoms are most significantly modulated in the monoclinic 
-direction to form an ordered arrangement. Such a positional modulation causes a quasi-periodic shift of Na atoms from the centers of the NaO
polyhedra between undulated CoO sheets, changing the form of the NaO polyhedron from an octahedral coordination (O) to a trigonal prismatic one (P). Where the Na atoms are most significantly shifted, the neighboring Na atoms are located at almost touching distances and yielding Na-deficient sites. As a result, a typical sequence of NaO octahedra with -O-O-O-P-
-P- along the a-axis is realized.
baddeleyite involving softenings of bulk modulus and atom vibrationsFukui, Hiroshi*; Fujimoto, Manato*; Akahama, Yuichi*; Sano, Asami; Hattori, Takanori
Acta Crystallographica Section B; Structural Science, Crystal Engineering and Materials (Internet), 75(4), p.742 - 749, 2019/08
Times Cited Count：14 Percentile：77.04(Chemistry, Multidisciplinary)Monoclinic ZrO baddeleyite exhibits anomalous softenings of bulk modulus and atom vibrations with compression. We have investigated the pressure evolution of the structure by neutron powder diffraction combined with ab-initio calculations. The present results showed that the anomalous pressure response of the bulk modulus is related not to the change in the bonding characters but to the deformation of an oxygen sublattice, especially one of layers made of oxygens in the crystallographic 
* plane. The layer consists of two parallelograms; one is rotating with little distortion and the other is being distorted with increasing pressure. This deformation of this layer makes one of Zr-O distances long, resulting in the softening of some atom vibrational modes.
Komatsu, Kazuki*; Shinozaki, Ayako*; Machida, Shinichi*; Matsubayashi, Takuto*; Watanabe, Mao*; Kagi, Hiroyuki*; Sano, Asami; Hattori, Takanori
Acta Crystallographica Section B; Structural Science, Crystal Engineering and Materials (Internet), 71(1), p.74 - 80, 2015/02
Times Cited Count：20 Percentile：79.24(Chemistry, Multidisciplinary)Magnesium dichloride decahydrate (MgCl10HO) and its deuterated counterpart (MgCl10DO) are identified for the first time by in-situ powder synchrotron X-ray and spallation neutron diffraction. These substances are crystallized from a previously unidentified nanocrystalline compound, which originates from an amorphous state at low temperature. A combination of a recently developed autoindexing procedure and the charge-flipping method reveals that the crystal structure of MgCl 10HO consists of an ABCABC... sequence of Mg(HO) octahedra. The Cl
anions and remaining water molecules unconnected to the Mg
cations bind the octahedra, similar to other water-rich magnesium dichloride hydrates. The D positions in MgCl10DO, determined by the difference Fourier methods using the neutron powder diffraction patterns at 2.5 GPa, show the features such as bifurcated hydrogen bonds and tetrahedrally coordinated O atoms.
-thiolactam formation in the crystalline stateHosoya, Takaaki*; Uekusa, Hidehiro*; Ohashi, Yuji*; Ohara, Takashi; Tanaka, Ichiro*; Niimura, Nobuo*
Acta Crystallographica Section B; Structural Science, Crystal Engineering and Materials (Internet), 62(1), p.153 - 160, 2006/02
Times Cited Count：5 Percentile：48.15(Chemistry, Multidisciplinary)Since N,N-dibenzyl-1-cyclohexenecarbothioamide is photoisomerized to the optically active -thiolactam with the retention of the single-crystal form, the mechanism of chirality induction was identified by X-ray crystal structure analyses during the process of the reaction. In order to clarify the mechanism of hydrogen transfer in the reaction, the H atomsof the benzyl groups were replaced with deuterium atoms. The crystal structure after photoisomerization was analyzed by neutron diffraction. One of four deuterium atoms of the two benzyl groups is transferred to the C atom of the cyclohexene ring. The absolute configuration of the -C
HD- group(chiral methylene) in the photoproduct r-thiolactam revealed that the deuterium atom occupies the equatorial position. This suggests that the deuterium atom is not transferred from the benzyl group of a neighbouring molecule, but from one of the benzyl groups within the molecule.
O
)below the verwey transition temperature; T.F.Koetzle*; ; ; ;
Acta Crystallographica Section B; Structural Science, Crystal Engineering and Materials (Internet), 38(8), p.2121 - 2133, 1982/00
Times Cited Count：256 Percentile：99.44(Chemistry, Multidisciplinary)no abstracts in English
; Masaki, N.
Acta Crystallographica Section B; Structural Science, Crystal Engineering and Materials (Internet), 31(6), P. 1793, 1975/06
Times Cited Count：19no abstracts in English
O
by Neutron Diffraction;
Acta Crystallographica Section B; Structural Science, Crystal Engineering and Materials (Internet), 28(3), p.785 - 791, 1972/03
Times Cited Count：41no abstracts in English
O
Masaki, N.;
Acta Crystallographica Section B; Structural Science, Crystal Engineering and Materials (Internet), 24(10), p.1393 - 1394, 1968/00
Times Cited Count：11no abstracts in English
