ABINIT

ABINIT is a free software package for physicists, distributed under the GNU General Public License, whose main program allows the total energy, charge density, and electronic structure of systems made of electrons and nuclei (molecules and periodic/crystalline solids) to be calculated within Density Functional Theory (DFT), using pseudopotentials, and a plane wave basis.

ABINIT also includes options to
 * optimize the geometry according to the DFT forces and stresses;
 * perform molecular dynamics simulations using these forces; and
 * generate dynamical matrices, Born effective charges, and dielectric tensors.

Excited states can be computed within the Time-Dependent Density Functional Theory (for molecules), or within Many-Body Perturbation Theory (the GW approximation). In addition to the main ABINIT code, different utility programs are also provided.