Welcome to the Glass Age

201 a disordered atomic structure. As recognized already by Zachariasen in 1932, structural disorder creates an excess volume over the ordered state. This is visible when comparing crystalline and glassy forms of silica, but also neatly arranged versus freely moving objects. As a result, a disordered structure becomes non-affine at a certain length scale of observation; at this length scale, it comprises spatially fluctuating properties, thus, an end to structural homogeneity. Interestingly, many of the macroscopic characteristics we usually attribute to glasses rely on exactly this interplay of long and intermediate range homogeneity on the one side, and locality on the other: the way glasses break, the way they are optically transparent or the way they transmit sound. Entering into a new phase of glass technology, it will be a major challenge to elucidate order in disorder. Universal descriptors and quantifiers will need to be deciphered towards the predictability of non-affinity beyond individual classes of materials [6]. These will allow for a new level of material design. Processing strategies adapted to such new generations of glasses will enable a world of novel glass products, further strengthening this exciting material’s indispensable role towards a sustainable future. Figure 13.3. Order-disorder competition at a glass-like surface. Source: L. Wondraczek.