Instability of the Crystal State

It has long been known that, beyond a certain size, the crystal becomes unstable,  favouring an amorphous, hence disordered structure. The critical size obviously depends on the material. For example, in the case of silicon, a theoretical study has shown that this crystalline–amorphous transition occurs for sizes of the order of 3nm. This same study stresses that this phase transition is discontinuous. It is therefore quite appropriate here to speak of a grain size dependent phase transition.  The size of a nanocrystal thus plays the role of a kind of intensive quantity imposing the crystalline or amorphous state in the same way as the temperature or the pressure.