Contribution of powder diffraction for structure refinements of aperiodic misfit cobalt oxides
Contribution of powder diffraction for structure refinements of aperiodic misfit cobalt oxides
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DOI：
10.1107/s0021889804018096
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发表时间：
2004-10-01
影响因子：
6.1
通讯作者：
Petrícek, V
中科院分区：
文献类型：
--
作者：
Grebille, D;Lambert, S;Petrícek, V
两个家庭的错配钴氧化物已重新研究使用中子和同步辐射粉末衍射数据和Rietveld结构的非周期性结构的四维形式主义的改进。在第一个系统[Ca 2CoO 3][CoO 2]（1.62）中，先前从单晶衍射数据描述的两个复杂多型相的结构特异性特征已经被证实为该系列的主项，并且用C2/m（1，delta，0）s 0超空间对称性（R-p = 0.026，R-wp = 0.031，R-B = 0.014）描述。高分辨率的同步辐射衍射实验已被解释与结构的三斜畸变，可能与本征调制的[Ca 2CoO 3]亚晶格与Co和O分裂原子的网站。在第二个体系Ca-0.82（Cu_（0.65）Co_（0.35）O_2）中，金属中心的一个新的占位调制具有Fmmm（α_（11））0 ss超空间对称性（R-p = 0.031，R-wp = 0.039，R-B = 0.027），并与阳离子中心的平方配位的原子间距离调制有关.在这两种情况下，最近开发的工具，使用粉末衍射数据（在JANA 2000包）的非周期性系统的结构细化已经证明了他们的效率，特别是作为特定的补充，以前的单晶结构细化。
Two families of misfit cobalt oxides have been reinvestigated using neutron and synchrotron powder diffraction data and Rietveld structure refinements in the four-dimensional formalism for aperiodic structures. In the first system [Ca2CoO3][CoO2](1.62), the structure-specific features of two complex polytypic phases previously described from single-crystal diffraction data have been confirmed for the main term of the series and are described with the C2/m(1,delta,0) s0 superspace symmetry (R-p = 0.026, R-wp = 0.031, R-B = 0.014). The high-resolution synchrotron diffraction experiments have been interpreted with a triclinic distortion of the structure, probably related to an intrinsic modulation of the [Ca2CoO3] sublattice in relation with Co and O split atomic sites. In the second system Ca-0.82(Cu0.65Co0.35O2), a new occupation modulation of the metallic site is shown with the Fmmm(alpha11) 0ss superspace symmetry (R-p = 0.031, R-wp = 0.039, R-B = 0.027) and is interpreted in relation with the modulated interatomic distances of the square coordination of the cationic site. In both cases, recently developed tools for structure refinements of aperiodic systems using powder diffraction data ( in the JANA2000 package) have proved their efficiency, in particular as specific complements to previous single-crystal structure refinements.