metastability

Metastability is a property of a system in which a configuration is locally stable but not the most stable possible state. In terms of energy, the system occupies a local minimum of the potential energy surface, separated from the global minimum by an energy barrier. Because overcoming the barrier is required for a transition to the lower-energy state, the metastable state can persist for long times even though it is not thermodynamically the equilibrium state. The lifetime of a metastable state depends on temperature, barrier height, and environmental conditions, and transitions can occur through thermal activation or, at very low temperatures, quantum tunneling.

metastable states are often described using the language of energy landscapes and kinetics rather than equilibrium thermodynamics alone. The observed persistence reflects a kinetic bottleneck: the system remains trapped in a local minimum until fluctuations provide sufficient energy to cross the barrier or until a different pathway lowers the barrier.

Common examples span multiple disciplines. In chemistry, supercooled liquids and supersaturated solutions are metastable relative to crystallization or precipitation. In condensed matter, rapidly quenched crystals or amorphous solids may occupy metastable arrangements; glasses are often regarded as kinetically trapped, non-equilibrium states. In geology and metallurgy, diamond is metastable with respect to graphite under ambient conditions, and certain alloy phases are metastable after quenching. In physics, false vacuum states can persist and decay by bubble nucleation or tunneling.

Metastability is a central concept for understanding material properties, phase transitions, and the dynamics of complex systems. It provides a framework for predicting when and how systems will evolve toward true thermodynamic equilibrium.