| 单词 | icosahedron |
| 释义 | icosahedron A polyhedron having 20 triangular faces with five edges meeting at each vertex. The symmetry of an icosahedron (known as icosahedral symmetry ) has fivefold rotation axes. It is impossible in crystallography to have a periodic crystal with the point group symmetry of an icosahedron (icosahedral packing). However, it is possible for short-range order to occur with icosahedral symmetry in certain liquids and glasses because of the dense packing of icosahedra. Icosahedral symmetry also occurs in certain quasicrystals, such as alloys of aluminium and manganese |
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