This may lead to cation ordering, redox reactions or other transformation processes that are likely to render the crystals in a different state than that prior to metamictization. The anisotropic oxygen and rare-earth element displacements observed in this crystal indicate a local domain structure of \(P2_1/a\) symmetry, when compared to the \(P2_1/a\) symmetry of the synthetic perrierite \(\hbox \)C or higher (Sokolova et al. The perrierite-(Ce) described in this study crystallizes in space group C2/ m. In such cases, it is generally not expected to rise above two. It can drop to zero in perrierite-type structures rich in Sr or Ca. On average, the charge modulus is observed to be larger for the chevkinite-type module stacking. The rutile module is expected to carry a negative charge, compensated by a positive charge of the silicate module. Taking into account the modular character of the chevkinite minerals, based on a rutile and a silicate module, the preferred formation of either the perrierite or the chevkinite structure type is correlated with the formal charge of the rutile and silicate modules. The composition and crystal structure of this sample is discussed in relation to the known properties of the chevkinite group minerals and related synthetic compounds. Also included on the site are updates of bug fixes, conditions of use and prices, tips for displaying the structures, a gallery of images, a flash movie, and instructions for installing a ICSD server.Perrierite-(Ce) crystals from ejecta of the Laacher See volcano, Eifel, in Germany were studied by X-ray single-crystal diffraction and electron microprobe analysis. The demo version can be queried and accessed by a web-interface which allows multiple methods of searching, and the resulting crystal structures can then be viewed online (with the CHIME plug-in) or downloaded for viewing with other visualization software. This database contains a 3325 structure subset of the 76,480 inorganic structures as of 2004. This site contains a free demonstration version of the Inorganic Crystal Structure Database. ICSD Web: the Inorganic Crystal Structure Database.Crystal structure data are downloadable in CIF format, and users may upload crystal data as CIF or REF files. The database is searchable by text, words, elements, volume, or number of elements. This database is a sister to the American Mineralogist Crystal Structure Database (AMCSD) and contains all the data that is in the AMCSD as well as data that has been deposited by individuals and laboratories. The crystal structure information includes mineral name, specification, crystal chemical formula, space group, unit cell parameters, coordinates, thermal factors and occupancy of atomic positions as well as literature references on crystal structure determination. Each mineral can be searched by name, specification, crystal chemical formula, or crystal structure characteristics. This searchable database, maintained by the Russian Foundation of Basic Research, includes 4785 entries (2365 unique mineral names). Crystallographic Database for Minerals and Their Structural Analogues.The site also includes links to other webpages about crystal structures. The Java applet allows the user to rotate and change the size of the crystal. This website features interactive Java applets of a variety of crystal structures of minerals and non-minerals. Several different graphical representations, an interactive Java applet of the structure, and useful information about the lattices can be obtained by clicking on images of crystal structures. Naval Research Laboratory, offers a concise index of common crystal lattice structures, including those from minerals and non-minerals. The site is searchable by mineral, author, chemistry, or cell parameters and symmetry. The database is maintained under the care of the Mineralogical Society of America and the Mineralogical Association of Canada, and financed by the National Science Foundation. This site is an interface to a crystal structure database that includes every structure published in the American Mineralogist, the Canadian Mineralogist, and the European Journal of Mineralogy. American Mineralogist Crystal Structure Database.The following online resources contain files which can be downloaded for interactive viewing either from a stand-alone visualization software or viewed from the website as a Java applet.
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