1. Atomic structure

Natural metallic crystals have relatively simple geometric shapes, bounded by planes, and have been known for centuries. They can also be produced in the laboratory, for example by growth from a seed placed in a supersaturated solid solution. X-ray, neutron and electron diffraction show that the microscopic structure of such crystals is that of three-dimensional periodic arrays of atoms: this is known as crystalline structure. One of the most spectacular proofs of this crystalline structure are the images of metal tips obtained by emission microscopes (figure 1 ).

In reality, common metal samples do not resemble crystals, but if their surface is properly prepared and examined under the optical microscope, a granular structure known as microstructure...