ALL Compounds are Solids under suitable conditions of temperature and pressure.
Many exist only as solids. An infinite array of points in space, in which each point has identical surroundings to all others. The periodic arrangement of atoms in the crystal. Kepler proposed this in 1611, in August 1998 Prof. Thomas Hales of the University of Michigan announced a computer-based solution. Gervais Chapuis A really fun way to create your own 2D patterns with different lattice symmetries is the Crystal Structures by Prof. Winston Chan, University of Iowa Prof.