| Pentagonal bipyramid | |
|---|---|
 | |
| Type | Bipyramid, Deltahedra Johnson J12 – J13 – J14 |
| Faces | 10 triangles |
| Edges | 15 |
| Vertices | 7 |
| Vertex configuration | |
| Symmetry group | |
| Dihedral angle (degrees) | As a Johnson solid: 138.2°, 74.8° |
| Dual polyhedron | pentagonal prism |
| Properties | convex, composite, face-transitive |
In geometry, the pentagonal bipyramid (or pentagonal dipyramid) is a polyhedron with 10 triangular faces. It is constructed by attaching two pentagonal pyramids to each of their bases. If the triangular faces are equilateral, the pentagonal bipyramid is an example of deltahedra, composite polyhedron, and Johnson solid.
The pentagonal bipyramid may be represented as 4-connected well-covered graph. This polyhedron may be used in the chemical compound as the description of an atom cluster known as pentagonal bipyramidal molecular geometry, as a solution in Thomson problem, as well as in decahedral nanoparticles.