Brownian thermal noise from the mirrors, due to mechanical dissipation in the coating layers, represents the limiting factor to the sensitivity of current and future interferometric gravitational wave detectors. During the last decade significant experimental effort on amorphous coatings has led to little improvement. Moreover, there is a lack of fundamental understanding of this phenomenon, which is critically limiting the development of effective design tools for successful coating architectures. The present project addresses the problem of losses in coating materials following a modeling approach, integrating simulations and theory. Microscopic simulations will help to shed light on the processes responsible for dissipation in amorphous materials and glasses, building on the design of new materials but also on the development and optimization of the production processes to reduce thermal noise. This work aims at filling the gap between experiments and theory/simulations, opening the way to new technological developments such as the in-silico design of advanced materials. There is obviously the potential for a great impact in many fields. Indeed, mechanical dissipation is responsible for the limited quality factor of glass-based devices also in applications outside the field of GW detectors, such as in optomechanics, atomic clocks and gyroscopes, that may be used in several other fundamental physics experiments. Finally, this project will perfectly integrate with the growing effort within INFN on coating materials which plays a crucial role in the Virgo experiment. In particular, the full research program could be carried within the PISA section, in the framework of the Virgo Coating R&D collaboration.