2. Classification of materials based on structure Regularity in atom arrangement periodic or not (amorphous)

《材料科学基础》第四章 固体中原子及分子的运动——表象理论（Phenomenological laws）

2.5 Indices of crystal planes and directions I What's crystal planes anddirect ions? The atomic planes anddirections passing through the crystal arecalled(crystal) planes and directionsrespectively

5. 8 The Stress Around a Dislocation 1. Screw dislocation: Displacement:

(for one dimensional diffusion only 1. Infinite system 1. Formula

I Atom movement in sol ids mechanical movement thermal vibration (short-range migration) Thermal motion diffusion(long-range migration)

5. 19 Reaction between Dislocation Condition 1. Geometrical condition

Back stress exerted by obstacle on leading dislocation. (It is supposed to be a short-range-force.) nrbdx =tpbdx dx virtual displacement

By cottrell atmosphere model, we can explain the sharp yielding phenomenon

5.16 Dislocation in FCC crystals Perfect dislocation b =na, +nb. +nC