What term describes the natural process where an unstable material attempts to stabilize by changing its structure?

The process described in the question aligns with the concept of "decay." Decay refers to the natural breakdown or degradation of unstable materials as they seek to achieve a more stable state. This process can involve the decomposition of materials or changes at the molecular or atomic level, ultimately leading to a different structure that is more stable.

In contrast, the other terms do not effectively capture the essence of this natural ordering process. Reconstruction generally implies rebuilding something to its former state or enhancing its structure rather than a natural degradation process. Transformation suggests a change that doesn’t necessarily imply instability or the process of stabilizing. Alteration could encompass a variety of changes but lacks the specific connotation of striving for stability after instability.