Density-functional theory in materials science

Simulations of materials behaviour are an important component of materials development when measurements are indirect and gain from theoretical interpretation, when the 'ideal' experiment is impeded by technological limitations, or when novel concepts and possible routes to their practical implementation are explored. Empirical physical models can be specifically tailored and have been employed successfully for the first two tasks, but the transfer to new tasks beyond the original application requires careful parameter reassessment. Quantum mechanical models, on the other hand, afford an a priori parameter-free access to materials properties on the nanoscale. In particular the density-functional theory provides computationally efficient access to the electronic structure of materials in the electronic ground state. Derived quantities such as forces, stresses, and responses to external electric or magnetic fields allow for the calculation of atom arrangements, lattice constants, elastic tensors, polarisabilities, dielectric and piezoelectric constants, or conductivity of nanosized systems or of systems with nanoscale building blocks. After a short introduction to the fundamentals of density-functional theory the applicability and the limitations of the approach for condensed matter systems will be discussed.