Multiscale modelling of irradiation-driven processes for emerging technologies
CECAM-HQ-EPFL, Lausanne, Switzerland
Irradiation-driven chemistry (IDC) is central to many modern technologies with high socioeconomic impact, such as surface deposition techniques, nanofabrication and nanolithography , 3D nano-printing , and novel light sources . All these technologies exploit irradiation of molecular systems and condensed materials which results in an alteration in the systems’ structure and morphology and hence changes in their electronic, mechanical and catalytic properties on both the nano- and the microscale. The interaction of different radiation modalities (UV light, X-rays, electrons, ion beams) with molecular systems initiates quantum processes (electronic excitation, ionisation, photon emission, radiation-induced fragmentation), electronic and thermal relaxation of deposited energy as well as transport of different species (secondary electrons, atomic and molecular fragments) produced in the irradiation process. These quantum transformations are followed by the next stage that includes the IDC leading to subsequent induced transformations of molecular systems. This complex cascade of IDC processes takes place on different time and spatial scales and its understanding must be based on a multiscale approach that treats the entire multistage scenario in a consistent manner. Such an approach must combine various theoretical and experimental methods into a coherent framework whilst going beyond the limitations of the particular methods [4,5].
The efficient and reliable coupling of quantum-mechanical (e.g., based on DFT and TDDFT) and classical molecular dynamics (MD) approaches is still an open question being in its infancy. One of the principal issues in QM-MD coupling is the dynamical exchange of probabilistic QM and the deterministic classical MD information in the course of simulations, which is especially essential when considering the interaction of various radiation modalities with the matter.
Another bottleneck of computational physics dealing with the transport of radiation through the matter concerns the deficiency of the Monte Carlo (MC) methods, that are widely used in this area of research, to account properly for the dynamics of the medium induced by its irradiation. The medium response to irradiation can be very strong as known, e.g., from ion-beam surface sputtering , or nanoscale shock waves induced in the vicinity of ion tracks or caused by intensive laser irradiation of various targets [4,7,8]. These examples indicate the need for a link between MD and MC methods for the efficient simulations of dynamics (including chemistry) of complex molecular systems under irradiation. Initial steps in this direction were made by means of a novel computational method - Irradiation-Driven Molecular Dynamics [4,9], which was applied to atomistic modelling of the formation of metal nanostructures in the process of focused electron beam induced deposition , or chemical transformations in the medium in the vicinity of ion tracks .
The resolution of the aforementioned and other existing bottlenecks in the field requires strong synergies of the experts in computational modelling with different background, experimentalists and technologists, capable of validating the outcomes of computational modelling and building closer ties to the concrete technological applications. Establishing such synergies will be among the main goals of the envisaged workshop.
Andrey Solov'yov (MBN Research Center) - Organiser
Alexey Verkhovtsev (MBN Research Center gGmbH) - Organiser
Nigel Mason (The University of Kent) - Organiser