John Harris

The density functional scheme is now the standard method used to compute energies, equilibrium geometries and vibration frequencies in molecular and condensed-matter chemistry. Applications to mechanical properties of materia1s are less well established. Early work was limited to the lattice constants and bulk moduli of eiemental materials or binary alloys. Computations of the full stiffness matrices of materials began to appear in the literature only in the 1990's. I give a brief review of the state of the art and demonstrate that the density functional scheme does give accurate results for the stiffness matrix. I also outline practical ways of computing thermo-elastic properties such as the thermal expansion coefficient. These remain to be tested.