Periodic Reporting for period 4 - UTOPES (Unifying concepts in the topological design of non-crystalline materials) Reporting period: 2021-03-01 to 2022-02-28 Summary of the context and overall objectives of the project Glasses have traditionally been enabling materials in major societal challenges. Significant breakthroughs on many areas of technological progress have been very closely linked to the exploitation of glassy materials. This key role will persist in the global goals for a sustainable future, from living, energy, health and transport to information processing. However, fundamental limitationsmust be overcome on this road.As a major, ab initio exploitation of disordered materials must be achieved, using highly-adapted processing strategies. Such technologies will not only enable new types of glasses with unprecedented properties, but also novel processing routes that might overcome current limitations of energy efficiency. To this end, fundamental research and in-depth conceptual developments are required which combine the formulation of chemical compositions, knowledge of structural evolution on molecular scale, and the thermo-kinetics of material deposition into holistic design tools. Such tools would significantly contribute to solving some of the most urgent material needs for glass applications, be it in the form of thin films, particles or bulk products.The UTOPES project challenged today’s engineering concepts towards the conception of such tools. For that, melt deposition, isothermal deposition from liquid phases, and gas-phase deposition of non-crystalline materials were considered in a generalist approach, which was to overcome traditional boundaries between classes of chemically different materials. As a unifying assumption, we started from ideas of structural disorder being determined not only by the chemical constituents present in the material, but also by the way a given glass was processed. In turn, such disorder – non-periodic fluctuations in local material behaviour on very short length scale – is the basis of macroscopic properties, and presents the primary difference to crystalline materials. Our starting point was the lack of quantifiers for disorder in chemically complex glasses: current theory is based on strongly simplified (both in terms of system size and species complexity) computational or physical models, whereas such models cannot cover phenomena known to occur in real-world, industrially relevant glasses. In turn, the latter are described mostly through short-range structural parameters, or through simplistic or empirical approaches which do not allow to connect disorder to macroscopic properties.Within UTOPES, we demonstrated how the evolution of disorder and structural complexity in glassy materials can be tailored through adequate processing. Providing a topological scheme for the quantification of disorder, we were able to resolve similarities for the broadest range of industrially relevant glass chemistries, from classical silicates to metallic, organic and hybrid materials – with a focus on refractory oxide glasses for future applications in optics and other functional devices. While fabricating such glasses through classical melting procedures leads to rigid trends in material disorder (and, hence, resulting properties), alternative processing can overcome such trends. For example, gas-phase deposition of refractory oxide glasses can achieve optical or mechanical properties outside of what is feasible by regular melting and annealing. UTOPES took us a great step further on the road to deciphering order in disorder, breaking grounds for the third generation of glasses with properties beyond the current limits of engineering. Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far The focus of our work was on the exploitation of the extremes of material deposition, in situ observation of the deposition process, the analysis and, ultimately, design of the resulting material properties, and the demonstration of examples-of-principle. This work was supported through analytical and numerical computational tools developed for parametrizing disorder statistics and intuitive visualization. We developed high-temperature physical gas-phase deposition as well as chemical vapour deposition to generate unconventional refractory glasses, deposition from solutions for the observation of colloidal glass transition processes, glass formation from zeolites and metal-organic frameworks through structural collapse reactions, and pressure-assisted or autoclave and ion-exchange synthesis of glassy states not accessible by conventional means; methods which all lie outside of the processing window of classical melting.On these primary lines, we developed an understanding of glasses being determined by disorder statistics, which form the basis of macroscopic behaviour. Similar to granular media, glasses are characterized by spatial fluctuations in structural cohesion; we quantified alternating regions of soft and hard modes such as previously known from computational models, on real-world glasses. Our observations revealed that disorder underlies rigid correlations between its extent and the characteristic length scale: classical melting does not allow for notable tailoring of disorder beyond a line. Only non-classical ways to obtain glasses allowed us to decouple processes of structure formation such as they occur during regular melt deposition. In this way, novel states of glass could be generated, for example, by entropic rejuvenation of non-metallic glasses using ultra-fast heat extraction as a means to fabricate objects at viable scale with enhanced mechanical properties – currently exploited for further application in the form of thin-walled glass products. On the other extreme, low-entropy glasses derived by gas-phase deposition at elevated temperature, otherwise available only hypothetically through very slow cooling processes. Such glasses with strongly reduced structural disorder widen the property space for optical applications.Such links between disorder statistics and macroscopic behaviour do not only provide a fully new avenue for glass design. Knowledge of disorder can also be used for the reconstruction of high-throughput computational proxies, from which property statistics and glass topology can now be predicted. Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far) Through combining in-depth analyses of the evolution of disorder and molecular structure during non-conventional material deposition with process-tailoring and compositional optimization, UTOPES broke grounds for the third generation of glass technological exploitation, i.e. conceiving new, industrially relevant glass materials based on ab initio understanding. To this end, a unified approach was established in terms of connecting hitherto separated areas of glass chemistry. Starting from inorganic oxide materials, we were able to bridge our understanding towards the emerging class of organic-inorganic hybrids, opening avenues for generalist schemes of glass deposition processes covering melt deposition, isothermal deposition from liquid phases, and gas-phase deposition. As the connecting feature in this broad landscape of processes and chemical compositions, we exploited theories on the statistics of disorder and spatially fluctuating properties. We were able to establish ways for their direct and universal application on real-world materials, overcoming the limitations of simplified models towards quantitatively relating glassy disorder to practical material behaviour. Such understanding is paving the way for new glass products, applications and fabrication methods. picture-public.jpg
