| Grain boundaries are interfaces in solids that profoundly influence the mechanical properties of materials at all length and time scales. We have analyzed the structure of 44 symmetric tilt grain boundaries in aluminum in the light of the structural unit model through a series of atomistic simulations. The minimum energy structure as predicted by the structural unit model does not always coincide with the results of our computations. In order to solve this discrepancy, we have proposed an effective Hamiltonian for grain boundaries which successfully computes the energy of an interface by summing over interaction potentials between neighboring structural units. We have also investigated the role of grain boundaries in energy dissipation in microresonators. We have proposed two models for this behavior, one of which is a viscous sliding model. The other is a computational model based on the approximation of a low-angle tilt grain boundary as an array of edge dislocations. By accounting for all the forces that act on the dislocations, we carry out a dynamic simulation of the motion of the interface. This enables us to compute the quality factor of the resonator as a function of microstructural and geometric parameters of a vibrating beam. |
