Doctoral defence: Ye Wang "Investigating the properties of metal surfaces under high electric fields based on ab initio calculations"

On January 15th at 15:15 Ye Wang will defend her doctoral thesis "Investigating the properties of metal surfaces under high electric fields based on ab initio calculations" for obtaining the degree of Doctor of Philosophy (in Physics).

Supervisors:
Professor Veronika Zadin, University of Tartu
Professor Alvo Aabloo, University of Tartu
Associate Professor Sergei Vlassov, University of Tartu
Associate Professor Andreas Kyritsakis, University of Tartu

Opponent:
Associate Professor Roberto Luis Iglesias Pastrana
Department of Physics, University of Oviedo, Spain

Summary:
High electric fields significantly influence the behavior of metal surfaces, leading to complex changes in interatomic interactions. These interactions can drive various electric field-induced surface modifications, including biased surface diffusion and surface restructuring. The study focused on developing atomic-level simulation models to investigate these electric field-induced surface modifications. The growth of nano protrusions on metal surfaces by biased diffusion is considered one of the most plausible explanations for vacuum breakdown initiations. Previous theories suggest that atomic diffusion is biased toward directions with stronger electric field gradients. Although the MD FEM method was used to validate this hypothesis, it demonstrated only qualitative agreement, confirming that atomic diffusion favors directions with stronger field gradients. However, achieving quantitative agreements requires further development of more precise methods. The field surface dynamics are described by the effective dipole moments and polarizability, with the question of the significance of hyperpolarizability terms, in this study, it has been proven that hyperpolarizability terms are negligible within the relevant field range (<15 GV/m). Given the limited experimental evidence on field-induced surface modifications, a recent experimental finding may support this hypothesis. The experiment showed a 10% field emitted current on the WC surface, whereas a current of only 1% would typically be expected for such a monostep structure. This study revealed the atomic structure of the WC surface, laying a solid foundation for further investigations into field-induced surface restructuring.