In amorphous solids (literally “solids without form” or non-crystalline solids) the particles do not have a repeating lattice pattern. They are also called “pseudo solids.” Amorphous materials have an internal structure made of interconnected structural blocks. These blocks can be similar to the basic structural units found in the corresponding crystalline phase of the same compound.
The amorphous solids are formed due to particular conditions during the solidification process (for example by increasing the cooling speed), which do not allow the atoms to stabilize thermodynamically in an ordered condition, thus preventing the formation of a periodic crystal structure. Amorphous solids are isotropic.
Examples of amorphous solids include glass, rubber, gels, and most plastics. An amorphous solid does not have a definite melting point; instead, it melts gradually over a range of temperatures, because the bonds do not break all at once. This means an amorphous solid will melt into a soft, malleable state (think candle wax or molten glass) before turning completely into a liquid.
Amorphous solids have no characteristic symmetry, so they do not have regular planes of cleavage when cut; the edges may be curved. They are called isotropic because properties such as refractive index, conductivity and tensile strength are equal regardless of the direction in which a force is applied.