Equilibrium statistical mechanics of grain boundaries

• A bicrystallography-based framework is developed to span the microstate configuration space of grain boundaries. • Grain boundary microstates are linked to physically meaningful defect content in the form of intrinsic disconnections. • A statistical mechanical formulation is used to compute grain boundary free energy, internal energy, and entropy. • The framework identifies known grain boundary ground states and yields competing metastable microstates. • Grain boundary phase diagrams are obtained from free energies.