[SY-G2] Symposium G-2

[SY-G2] Multiscale-multiphysics simulations of metal nanotips under high electric field

^○Mihkel Veske¹, Andreas Kyritsakis¹, Kyrre Ness Sjobak², Vahur Zadin³, Flyura Djurabekova¹ (1.Helsinki Institute of Physics, University of Helsinki, Finland, 2.Department of Physics, University of Oslo, Norway, 3.Institute of Technology, University of Tartu, Estonia)

We propose a method for efficiently coupling the finite element method with atomistic simulations like molecular dynamics or kinetic Monte Carlo. Our method enables to dynamically build an unstructured mesh with optimized density that follows the geometry defined by atomistic data. On this mesh, multiphysics problems can be solved to obtain distribution of physical quantities of interest, which can then be fed back to the atomistic system. The simulation flow is optimized to maximize computational efficiency while maintaining good accuracy.

We use this method to simulate the evolution of nanostructures under high electric field. By solving Poisson equation, we obtain the 3D distribution of electric field around the nanostructure. Using the field, we calculate electron emission currents, surface and space charge and electrostatic forces for surface atoms. By taking Joule and Nottingham heating into account and solving 3D heat equation, we also obtain atomistic velocity perturbation.

Our method has shown remarkable overlapping with an analytical solution and has proved to be efficient and robust enough to simulate large-scale thermal runaway processes. Using those simulations, we demonstrated for the first time the disintegration of Cu nanotip in extreme field conditions. This process is widely believed to lead to the formation of plasma and cause vacuum arcing in high gradient structures.