Quantum ESPRESSO is an integrated suite of open-source computer codes for quantum simulations of materials using state-of-the-art electronic-structure techniques, based on density-functional theory, density-functional perturbation theory, and many-body perturbation theory, within the plane-wave pseudopotential and projector-augmented-wave approaches. A recent JPCM paper describes recent progress and advances on this software. We caught up with author Paolo Giannozzi to find out more in his own words.
Numerical simulations “from first principles” – i.e., starting from the electronic structure of the system at hand – have become widespread in science and technology. This is especially true for simulations based on density-functional theory, plane waves, and pseudopotentials. Even many non-specialists use, or produce, results from simulations in the most diverse fields to interpret experimental data, to improve existing models, or to build new ones. The success of first-principles simulations relies on the continuous improvement of theoretical methodologies and of algorithms, as well as on the increase of computer power. These factors would be however of little practical impact without the broad availability of efficient and reliable software implementing new methodologies and exploiting the performance of modern (super-)computer architectures.
The increasing complexity of theories, methodologies, and algorithms is making the development of scientific software, or even its simple maintenance, a hard-to-meet challenge for any single scientist or research group. Developing state-of-the-art scientific software requires a deep knowledge of the core science, combined with expertise in numerical analysis, computer architectures, and software engineering. Unfortunately, the investment in the development and maintenance of scientific software has historically lagged behind, compared to the investment in other infrastructural efforts that support the scientific community. This is even more noteworthy, and inexplicable, given the benefits of open-source software.
The Quantum ESPRESSO (QE) distribution is a long-established broad effort aiming to provide to the scientific community an open-source, efficient, and extensible software framework, with which state-of-the-art calculations can be performed and new ideas and methods can be implemented and tested. QE in its present form has been distributed for the last 15 years, but its origins date back to the mid 1980’s, when ground-breaking methodologies such as Car-Parrinello molecular dynamics and density-functional perturbation theory were developed and first implemented in codes that have now evolved into QE core components. Currently, QE contains several inter-operable packages, going from the core functionalities necessary to anyone doing quantum simulations, to advanced techniques and new developments for a few specialists.
This paper describes the methodological and algorithmic advances that have been achieved in the last 10 years, notably since the publication of the first paper J. Phys.: Condens. Matt. 21, 395502 (2009) documenting the project. Notable advances include:
- New functionals. Non-local van der Waals functionals and explicit corrections for van der Waals interactions have been implemented, Hubbard-corrected functionals have been improved and extended, a new package implementing ACFDT-RPA has been added.
- Hybrid functionals. Significant performance improvements have been obtained with Adaptively Compressed Exchange and with localization of Kohn-Sham orbitals.
- Excited states, using time-dependent density-functional and many-body perturbation theories.
- Multi-scale modelling, with QM-MM and continuum embedding environments. On the algorithmic and software-engineering side, we also detail improved and extended parallelization, new file formats for easier and enhanced interoperability with other codes, workflow management, and improved code modularity.
The development effort is ongoing in all directions: new methods and faster algorithms, porting to new computer architectures, better code management, verification and validation, following the stated goal for Quantum ESPRESSO to continue to offer to the community powerful scientific software for ever more powerful science.
Call for Papers
Following the publication of this recent article Advanced capabilities for materials modelling with Quantum ESPRESSO in the JPCM Computational and Experimental Methods section, we are issuing a call for papers and letters on Computational Electronic Structure methods, including novel applications of existing applications, and advances in methods.
About the Author
Paolo Giannozzi is Associate Professor of Condensed-Matter Physics at the University of Udine. He graduated at the University of Pisa, obtained his Ph.D. at the University of Lausanne, then spent various periods at EPF Lausanne, Scuola Normale Superiore di Pisa, IBM Research Laboratories Zurich, CECAM Lyon, Princeton University. His research field is the developments of methodologies for density-functional theory and their application to nano-structures. He is currently coordinating the development of the Quantum ESPRESSO distribution of software, with a special interest in optimization, parallelization, validation and verification. He is 2013 Fellow of the American Physical Society, Division of Computational Physics.