DFT calculations of solids with LAPW and WIEN2k

In solids one often starts with an ideal crystal that is studied on the atomic scale at zero temperature. The unit cell may contain several atoms (at certain positions) and is repeated with periodic boundary conditions. Quantum mechanics governs the electronic structure that is responsible for properties such as relative stability, chemical bonding, relaxation of the atoms, phase transitions, electrical, mechanical, optical or magnetic behavior, etc. Corresponding first principles calculations are mainly done within density functional theory (DFT), according to which the many-body problem of interacting electrons and nuclei is mapped to a series of one-electron equations, the so-called Kohn-Sham (KS) equations. One among the most precise schemes to solve the KS equations is the linearized-augmented-plane-wave (LAPW) method that is employed for example in the computer code WIEN2k to study crystal properties on the atomic scale (see www.wien2k.at). Nowadays such calculations can be done—on sufficiently powerful computers—for systems containing about 100 atoms per unit cell. A selection of representative examples and the references to the original literature is given.