Quartz Atomic Structure

This is the atomic structure of quartz, a low-pressure polymorph of SiO2. In each tetrahedron, a silicon atom is located at the center and four oxygen atoms are at the vertices.

By printing this model, you can understand the characteristics of quartz structure such as:
- a network made by chains of tetrahedron, which share the vertices,
- a helical symmetry (120° rotation with 1/3 translation along c-axis. "1/3" corresponds to a tetrahedra and c-axis is a vertical line),
- large voids anywhere in quartz.

This stl file is made by Blender with a self-made python script.
All atoms are supported by cylinders to avoid using automatic supports, which is cumbersome to remove in my 3D printer.