fictive temperature

The term "fictive temperature" relates to the structure of amorphous solids, or glasses. When a liquid cools, it transitions into a solid state. This transition occurs over a range of temperatures known as the glass transformation range. The fictive temperature represents the specific temperature at which the liquid's structure is effectively "frozen" into the glassy state.1

Unlike crystalline solids, which have a regular, repeating atomic structure, amorphous solids like glass have a more disordered, random atomic arrangement. The fictive temperature is a way to describe the thermal history of the glass, indicating the temperature the liquid was at when its structure became fixed. This concept is important because the properties of glass, such as its viscosity and density, are influenced by this frozen-in structure.231