GNOME

Noble metal clusters and nanoparticles are used in many applications, often making use of the outstanding optical properties, characterized by the surface-plasmon resonances. These properties depend sensitively on the environment that surrounds the clusters. However, little is known about the clusters' interaction with the environment beyond theoretical treatments using simplifying effective-medium approaches. In particular, the influence of the interface to solid matrices on the electronic structure and thus the optical properties is hardly understood. In the GNOME project, we combine calculations of structure and optical response with dedicated experiments to study the optical properties of small gold clusters in SiO2 and Al2O3. Molecular Dynamics and Density-Functional Theory (DFT) calculations, aided by the use of machine-learning techniques, will be used to obtain and analyze realistic geometries of the clusters and the surrounding matrix at the atomistic level. Time-dependent DFT in periodic formulation will be used to study the dependence of electronic and optical properties on the nature of the matrix and the chemical state of the interface. Optical spectroscopy of size-selected gold clusters in silica and alumina matrices will provide benchmarks for the validation of the theoretic models. Our results are expected to provide a general understanding of how the interface affects the electronic and optical properties of small metal clusters at an atomistic scale. The understanding thus obtained will greatly facilitate the conception of new applications of cluster-based materials and help to optimize existing applications.