Certain molecules, called “globular” molecules, when first solidified form what are called “plastic” crystals. They are called “globular” either because they may exhibit an approximate spherical symmetry about their center of structure or because they may be small enough or of such a shape as to appear spherically symmetric because of rotation. The first case might be exemplified by methane (CH4) which has the configuration of a regular tetrahedron. The second case might be exemplified by hydrogen chloride (HCL)
