Pentagonal bipyramid Pentagonal bipyramid It is a very compact structure consisting of equilateral triangular planes with a closed magnet arrangement. Each triangular plane has a Closed Packing (CP) structure. The crystallisation system is orthorhombic (I) and the APF=0,7236 More information about this polyhedron can be found at the link below: en.wikipedia.org/wiki/Pentagonal_bipyramid Elongated pentagonal bipyramid This structure can result from a Pentagonal bipyramid by removing whole linear chains from pentagonal base. We notice that in the triangular sides we have a Closed Packing (CP) sructure. The crystallisation system is orthorhombic (I) and the APF=0,7236 More information about this polyhedron can be found at the link below: en.wikipedia.org/wiki/Elongated_pentagonal_bipyramid Orthorhombic (I) Body-Centered unit cell. If we observe a side face we will see that each sphere is tangled with four spheres in the lower plane, two spheres in the same plane, and another four spheres in the upper plane, a total of 10 spheres. Thus, the cordination number is 10. The unit cell expressing this type of crystallization is the Orthorhombic (I) Body-Centered unit cell. To be clearer, the unit cell is expressed by the centers of the 8 spheres and they form a rectangular parallelepiped. In the center of this rectangular parallelepiped there is a sphere. In this parallelepiped there are a total of two whole spheres, (8 Χ 1/8) + 1 = 2. See the picture below: Calculation of the APF index. Pentagonal prism This structure can result from a Elongated pentagonal bipyramid by removing its two peaks . The crystallisation system is orthorhombic(I) and the APF=0,7236 More information about this polyhedron can be found at the link below: en.wikipedia.org/wiki/Pentagonal_prism Pentakis dodecahedron. (hexecontahedron ) Watch below the construction of a 60-sided crystal (Pentakis dodecahedron). To construct this structure a total of 12 pentagonal bipyramids required for the outer surface, while two more pyramids are required for the inner support web. The disadvantage of this structure is that it has a vacuum inside it. More information: https://en.wikipedia.org/wiki/Pentakis_dodecahedron
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