<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Chung Chieh</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The Archimedean truncated octahedron. III. Crystal structures with geometric units of symmetry m3m</style></title><secondary-title><style face="normal" font="default" size="100%">Acta Cryst. (1982). A38, 346-349</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">1982</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">https://doi.org/10.1107/S0567739482000722</style></url></web-urls></urls><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">All geometric units in crystal structures of space groups&amp;nbsp;&lt;i&gt;Im&lt;/i&gt;3&lt;i&gt;m&lt;/i&gt;&amp;nbsp;and&amp;nbsp;&lt;i&gt;Pm&lt;/i&gt;3&lt;i&gt;m&lt;/i&gt;&amp;nbsp;and two out of the three types in those of&amp;nbsp;&lt;i&gt;Fm&lt;/i&gt;3&lt;i&gt;m&lt;/i&gt;&amp;nbsp;have&amp;nbsp;&lt;i&gt;m&lt;/i&gt;3&lt;i&gt;m&lt;/i&gt;&amp;nbsp;symmetry, whereas the remaining one of&amp;nbsp;&lt;i&gt;Fm&lt;/i&gt;3&lt;i&gt;m&lt;/i&gt;&amp;nbsp;possesses&amp;nbsp;&lt;img align=&quot;bottom&quot; alt=&quot;{\bar 4}&quot; height=&quot;13&quot; src=&quot;https://journals.iucr.org/a/issues/1982/03/00/a20652//teximages/a20652fi1.gif&quot; width=&quot;7&quot;&gt;3&lt;i&gt;m&lt;/i&gt;&amp;nbsp;symmetry. Theoretically, a geometric unit of&amp;nbsp;&lt;i&gt;m&lt;/i&gt;3&lt;i&gt;m&lt;/i&gt;&amp;nbsp;symmetry has atoms arranged as a collection of these possible polyhedra: octahedron, cube, cuboctahedron, truncated octahedron, truncated cube, small rhombicuboctahedron and rhombicuboctahedron. All these can be derived from truncations, sometimes repeated, of the pair of platonic solids, cube and octahedron, which possess&amp;nbsp;&lt;i&gt;m&lt;/i&gt;3&lt;i&gt;m&lt;/i&gt;&amp;nbsp;symmetry. In reality, no known crystal structure has a geometric unit with a rhombicuboctahedron or a truncated cube. The close-packing requirement causes a complicated geometric unit to start (from the center) in one of the following ways: (i) a single atom followed by an octahedron, (ii) a single atom followed by a cube, (iii) an octahedron and (iv) a cube. The survey of structures indicates that polyhedra derived from an octahedron occur more frequently in real geometric units than those related to a cube.</style></abstract></record></records></xml>