Quantum ESPRESSO is an integrated suite of computer codes for electronic-structure calculations and materials modeling at the nanoscale. It is based on density-functional theory, plane waves, and pseudopotentials (both norm-conserving, ultrasoft, and PAW).

Quantum ESPRESSO stands for opEn Source Package for Research in Electronic Structure, Simulation, and Optimization. It is freely available to researchers around the world under the terms of the GNU General Public License.

Quantum ESPRESSO builds onto newly-restructured electronic-structure codes (PWscf, PHONON, CP90, FPMD, Wannier) that have been developed and tested by some of the original authors of novel electronic-structure algorithms - from Car-Parrinello molecular dynamics to density-functional perturbation theory - and applied in the last twenty years by some of the leading materials modeling groups worldwide. Innovation and efficiency is still our main focus.

Quantum ESPRESSO has evolved into a distribution of independent and inter-operable codes in the spirit of an open-source project. The Quantum ESPRESSO distribution consists of a "historical" core set of packages and a set of plug-ins that performs more advanced tasks. Researchers active in the field of electronic-structure calculations are encouraged to participate in the project by contributing their own codes or by implementing their own ideas into existing codes.

Quantum ESPRESSO is an initiative of the DEMOCRITOS National Simulation Center(Trieste) and SISSA (Trieste), in collaboration with the CINECA National Supercomputing Center in Bologna, the Ecole Polytechnique Fédérale de Lausanne, Princeton University, the Massachusetts Institute of Technology, and Oxford University. Courses on modern electronic-structure theory with hands-on tutorials on the Quantum ESPRESSO codes are offered on a regular basis in developed as well as devoloping countries, in collaboration with the Abdus Salam International Centre for Theoretical Physics in Trieste.