HOW TO GO FROM GAS TO LIQUID TO SOLID: _Amorphous states_ “’ In contrast to crystalline materials, their constituent atoms do not form ordered structures of repetitive motifs, but instead irregular ‘‘networks.’’ An idea of the ‘‘amorphous state’’ can be obtained when considering the formation process of a solid. The starting point is a high-temperature gas of individual atoms/molecules. Upon reduction of the temperature (at constant pressure), the volume shrinks, that is, the particles come closer to each other and start to interact. If the temperature reaches a critical value, the condensation point TC, the gas collapses into a liquid. The mutual attractive interactions between the particles dominate over their thermal energy, which drives them apart. In the liquid state the particles are still mobile, but move statistically with a mean free path length not longer than their own diameter. Further reduction of the temperature leads to solidification of the liquid; the particles at most vibrate about a fixed point in space, but do not leave it anymore. Along the described temperature trajectory the dynamics of the particles and their entropy decreases, while the order among them increases. It is considered a higher state of order, to know where a particle can be found.” SURFACE AND INTERFACE STUDIES, VOLUME 3+4

“Amorphous solids are metastable, their preparation is always kinetically controlled, and thermal activation will change their structure because under the same thermodynamic conditions there is always a more stable state, which – single or multiphase – consists of crystalline material. In principle, at T > 0 amorphous systems will always tend toward the global energy minimum. In practice, however, these systems are nonergodic, that is, during the observation period they will not leave their respective local energy minimum; their structure will not change. “

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