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Acta Cryst. (2014). A70, C1076
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It is known that different unit cells can have the same computed lines in some cases (Figure). The phenomenon was first called geometrical ambiguity and studied in [1]. In all the high-symmetric cases provided in [1], such unit cells correspond to derivative lattices of each other. Although this is not true in general for 3-dimensional lattices, this has been assumed in methods to search for geometrical ambiguities (e.g., [2]). Thus, a method to obtain all the geometrical ambiguities in very short time for a given unit cell parameters is provided. Because such a method has not been used for powder indexing, it will have impact in the following sense: firstly, it is useful for checking powder indexing solutions promptly. Some powder auto-indexing methods cannot obtain all the geometrical ambiguities. Even for the software including Conograph which can gain all the ambiguities, it is not straightforward to search for them from many indexing solutions using the figures of merit which are sometimes not reliable [3]. Secondly, the new method indicates that powder indexing has only finitely many solutions at least if peak search succeeds in obtaining all (but a few) diffraction peaks with q-values smaller than some calculated value. (Note that infinitely many solutions may exist for lattices of dimension more than 4.) The result seems to provide a foundation of automatic powder crystal structure analysis, because it is possible to obtain all the ambiguities by computation. The introduced method was implemented in the newest version of Conograph, which will be distributed on the web (http://research.kek.jp/people/rtomi/ConographGUI/web_page.html) by IUCr2014. ACKNOWLEDGEMENT: this research was partly supported by a JSPS KAKENHI grant (No.22740077) and by Ibaraki Prefecture (J-PARC-23D06).

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Acta Cryst. (2014). A70, C1172
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Since the operation start for J-PARC/MLF at 2008, neutron diffraction experiment using high intensity pulse neutron beam became possible. For example, if there are 1g typical oxide samples, it is possible to get one diffraction pattern in about ten minutes for `Rietveld-analysis-quality' at iMATERIA. Four neutron powder diffractometer, iMATERIA (IBARAKI Materials Design Diffractometer[1]), SPICA (special environment powder diffractometer dedicated for battery study), SuperHRPD (Super high resolution powder diffractometer, d/d = 0.03 %) and NOVA (high intensity total scattering diffractometer) are operating at J-PARC/MLF. In our previous neutron facility, the neutron intensity is not so strong to carry out routinely in operando neutron diffraction experiments. In J-PARC, however, it became possible to measure quickly changing neutron diffraction patterns in operando condition. iMATERIA is a versatile neutron diffractometer funded by Ibaraki prefecture for industrial application. In iMATERIA, Some user group was trying to in-situ measurements for battery. SPICA is optimized for an in operando neutron diffraction study to clarify the structural changes of battery materials at the atomic level. It has already typical results of time resolved measurements for a commercialized Li-ion battery. The structural changes of the material, which is dependent on the lithium content, were clearly observed. We will report the status of J-PARC/MLF diffractometers and recent result of in operando experiments.

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Acta Cryst. (2014). A70, C1362
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Glazer tilting system with tilting and rotation of oxygen octahedron, can describe ABO3 perovskite structure effectively. In highest symmetry, Pm-3m(No. 221) crystal structure is a0a0a0 without tilting and rotation. If temperature is lower, the different atomic radius of A and B causes tilting and rotation of BO6 octahedron. Glazer tiling notation of Pbnm(No. 62, cab lattice) orthorhombic structure is a-a-c+ with antiphase tilting along [110]cubic and in-phase rotation along [001]cubic for neighboring octahedron. SrRuO3 is rare example of itinerant ferromagnetic among 4d oxides. It shows zero thermal expansion, so called Invar effect below ferromagnetic transition(Tc=165 K). Otherwise, paramagnetic CaRuO3 has same Pbnm crystal structure without magnetic transition. To understand Invar effect and ferromagnetism of SrRuO3, We carried out high resolution Time-of-flight powder neutron diffraction using SuperHRPD beamline in J-PARC, with the best resolution Δd/d=0.03% of backscattering bank. Itinerant ferromagnetic SrRuO3 shows 50 fetometer increase of <Ru-O> mean bond below ferromagnetic transition while paramagnetic CaRuO3 shows decrease of <Ru-O> and follows well by the usual thermal expansion. For SrRuO3, Glazer tilting with deformation of RuO6 octahedron explains Invar effect and why lattice a is larger than lattice b in Pbnm structure. The increased <Ru-O> mean bond is considered as coupled order parameter with ferromagnetic transition. The band width of CaRuO3 is almost constant in the whole temperature range whereas ones of SrRuO3 decrease at low temperature. Then more localized Ru 4d orbitals probably contribute ferromagnetic transition.
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