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NANOMAT-Nanoteknologi og nye materialer

Gentic approaches to complex materials

Awarded: NOK 2.1 mill.

It might be argued that it is fruitful to interpret the average structure observed experimentally in disordered materials as a time and spatial average of the different local environments which are energetically accessible at a given temperature. The diff erent local structural environments correspond to separate local minima on the potential energy surface of the system. This "energy landscape" of the material is in simple terms a 3N-dimensional topographic map describing the interactions in the system. T he deepest valley on the map represents the global equilibrium structure, while other valleys represent local minima corresponding to higher-energy inherent structures. Using this simple landscape analogy, it is easy to see that also the dynamics of the s ystem relates to the potential energy hypersurface; the steepness of the valleys determines the vibrational amplitudes while the heights of the different hills (first order saddle points) separating the valleys (energy minima) suggests energetically favor able pathways between the different configurations and thus mechanisms for atomic motion. The landscape-picture is conseptually appealing, but it also emphasise the complexity of the landscape and stress additional difficulties which arises due to the la rge number of different local structures (many local minima) in disordered materials. We have shown that the genetic algorithm is a powerful tool for handling these problems. The present project aims at using a combination of genetic algorithms and appro priate secondary building entities in combination with other computational techniques to approach the potential energy hypersurface and especially the link between structure, energetics and ion conduction in fast-ion conductors. Also this methodology has potential for studies of design and prediction of hybrid inorganic-organic materials .Similar techniques will be used to approach grain boundaries as reservoirs of incompatible elements in ceramic.

Funding scheme:

NANOMAT-Nanoteknologi og nye materialer