Interfaces such as grain boundaries are ubiquitous in crystalline materials and have provided a fertile area of research over decades. Their importance stems from the numerous critical phenomena associated with them, such as grain boundary sliding, migration, and interaction with other defects that govern the mechanical properties of materials. Although these crystalline interfaces exhibit small out-of-plane fluctuations, statistical thermodynamics of membranes has been effectively used to extract relevant physical quantities such as the interface free energy, grain boundary stiffness, and interfacial mobility.

In this talk, I will put forward the viewpoint that monitoring thermal fluctuations of crystalline interfaces by way of molecular dynamics can serve as a computational microscope for gaining insights into the thermodynamic and kinetic properties of grain boundaries and present a rich source of future study. In particular, the talk will present how we use thermal fluctuations to estimate the grain boundary stiffness and mobility of grain boundaries by modeling them as Brownian particles.