Crystal Dislocation Glide — Peierls-Nabarro Model
Edge dislocations (extra half-plane of atoms) move through a crystal under applied shear stress.
Motion is resisted by the Peierls barrier (lattice periodicity) and viscous drag.
Dislocation velocity v = b(τ-τ_P)/B·sign(τ). Hall-Petch: σ_y ∝ d^(-1/2).