Materials are placed into categories to make them easier to classify when it comes to behaviour. Metals, plastics and rubbers are all categories that should be quite familiar. Amorphous materials are heard of less often but they are simply the materials in which there is no repeating structure that carries on throughout. Concrete and glass both fall into this definition. Some amorphous materials, when heated, become a viscous and more rubber like material. If they do this they are known as a “glass” although they are not all necessarily glass themselves. Viscous liquids can also undergo the phase change in reverse by being cooled very quickly they become brittle and form an amorphous solid, known as structural glasses, this process is called vitrification. The rapid cooling is necessary otherwise crystals would form and the liquid would simply freeze, however the slower the cooling rate, the lower the temperature is for a particular material for it to become a glass. It was pointed out by a Walter Kauzmann that if the transition temperature could be reduced to below absolute zero, then the cooling liquid would pass a point where it had less entropy than its own crystal form, despite crystals being the most stable form of any material. This is called the Kauzmann paradox and is often solved by introducing he concept of an “ideal glass.” Researchers have now presented a different idea that completely circumvents the Kauzmann paradox by introducing the idea of a “perfect glass.” A perfect glass bust be:
- Amorphous and completely uniform in this disorder.
- Lack an energy minima (most stable state) by the definition that if left to heat up would never crystallise.
- Possesses no freezing point, unlike the ideal glass model.
It it has been found that such a material is mathematically possible and now the primary concern is to discover if any real materials have some or perhaps all of the features.