Simulation of Dislocations in Metals - Introduction

Unlike covalently bonded substances, where the orientations of atoms maximize overlap of the valence orbitals, metallic bonds are non-directional. This means that the atoms will arrange themselves to maximize the number of nearest neighbors. Thus, many metal crystals have close-packed arrangements. In both the hexagonal and cubic closest packing lattices, each atom is surrounded by a hexagonal arrangement of six atoms (as illustrated in this demonstration), as well as three atoms above and three atoms below the hexagonal plane.

All crystal lattices have defects. When stress is applied, the number and nature of the defects changes, and the defects can move through the lattice, as illustrated in these demonstrations. The "Heat Treatment of a Metal Bobby Pin" series shows how metals can be treated to alter the number of dislocations, and illustrates how the number of defects influences the physical properties of the metal.