Topic: 2D Layered Hetrostructures
Minnesota AEM Team: Ilia Nikiforov, Ellad Tadmor
Other PIs: Efthimios Kaxiras (Harvard), Philip Kim (Harvard), Mitchell Luskin (U. Minnesota) (lead-PI), Hossein Mosallaei (Northeastern), Petr Plechac (U. Delaware)
Funding: Multidisciplinary University Research Initiative (MURI), Army Research Office, Department of Defense
Description: This proposal concerns the study of van der Waals bonded, layered heterostructures, using novel strongly linked multiscale computational methods, and guided by concurrent experiments that will both inspire the theory and benefit from its predictions. Layered heterostructures are a very new and active field of research that has emerged from recent advances in producing single layers of semi-metals (graphene), insulators (boron nitride) and semiconductors (transition metal dichalcogenides). The prospect of combining the properties of these layered materials opens almost unlimited possibilities for novel devices with desirable, tailor-made electronic, optical, magnetic, thermal and mechanical properties. The extremely broad range of structural and compositional choices demands an effective design tool, based on accurate and efficient computational methodologies across all relevant scales and property ranges.
The proposed research will develop efficient and reliable strongly-linked multiscale methods for coupling several scales based on a rigorous mathematical basis. Specifically: The coupling of quantum to molecular mechanics will be achieved by properly taking into account the mathematics of layer incommensurability. The coupling of atomistic-to-continuum will be achieved by methods that can reach the length scales necessary to include long-range elas- tic effects while accurately resolving defect cores. These methods will optimize the defect core size, model coupling, mesh refinement, and far field boundary conditions to enable the efficient computation at physically relevant length scales. To construct an accurate continuum model, more accurate Cauchy-Born methods will be developed that utilize all of the symmetries of the 2D crystal multilattices. New accelerated molecular dynamics and kinetic Monte Carlo methods specially tailored for the weakly interacting van der Waals heterostructures will be developed that can reach the time scale necessary for synthesis and processing by CVD and MBE. This will be achieved by breaking down the various components of the layered structures to units, whose interactions can be established from quantum mechanical methods and can then be coarse-grained to allow modeling at the mesoscale. The simulations will be linked to macro and electromagnetic modeling to understand the physics and bridge to experimental investigation.