Predicting the properties of materials: dream or reality?

Before new materials are used in commercial products their properties must be known. This information can be acquired from experiments. Properties can also be calculated even before the materials exist. One of the theories that can be used in these calculations is the density functional theory. Developments in this field are discussed with the aid of results obtained from the theory. These results relate to materials in the ground state: the different crystal structures of silicon at increasing pressure, the rearrangement of atoms at the surface of silicon, the consequences for the crystal lattice when oxygen is incorporated and the magnetic behaviour of iron-yttrium compounds. The theory can also be used, with some modification, for predicting the emission of light from GaAs/AlAs superlattices.