Supporting research communities with large-scale DFT in the next decade and beyond

First-principles quantum-mechanical simulations based on density-functional theory (DFT), are today used hand in hand with experiment to design new materials. Conventional DFT has a computational effort which increases with the cube of the number of atoms and this limits the practical size of calculations. ONETEP is a world-leading UK-developed software package which uses a linear-scaling framework to enable calculations on much larger scales, uniquely without loss of accuracy compared to traditional methods. Thus ONETEP offers unmatched capabilities for constructing and simulating more realistic models of materials and including their environment in multiscale simulations.
ONETEP has been developed from the beginning to take advantage of supercomputers. Due to its non-trivial formulation and wide-ranging functionality, it is a highly complex code consisting of around half a million lines of code.
ONETEP is an academic community code which emerged from CCP9, the Collaborative Computational Project for the electronic structure of condensed matter, bringing together academics across disciplines, and forming the UK branch of the European Psi-k Network. In 2016 ONETEP became the flagship project of CCP9 and free to UK academics. Industrial exposure to ONETEP has resulted from close collaboration with BIOVIA, which has enabled integration with their Materials Studio user interface. This has led to considerable commercial impact and new industrial collaborations. Beyond the UK, ONETEP is gaining in popularity with developers in Ireland and China and users in many countries in Europe as well as the USA, China, Mexico and South Africa.
As with all software, ONETEP needs to be continuously evolved and updated in order to stay at the cutting edge. This is particularly challenging for a large collaborative academic project that has evolved over two decades. Furthermore, a range of developments, such as excited states, electrochemistry, embedding and wavefunction methods, have required pervasive changes. Since they affect the core algorithms of the code, these changes have inevitably led to increased complexity. Thus the code now needs to adopt a new structure to ensure its continued growth. At the same time it is important to maintain and further widen the community of users and developers to fulfill its primary objective to cater for the needs of the scientific community.
This project is targeted towards these two interconnected aims. It will re-engineer the code in its entirety, rationalising internal structure to allow further development and enhance the interoperability of existing functionality. Modern software engineering principles will be followed throughout, in close collaboration with the computational physics and chemistry groups of STFC SCD and research software engineers in Southampton, Warwick and Imperial. At the same time developments of new functionality to enable large-scale calculations of crystalline and semicrystalline materials will satisfy a demand in this area by many researchers, such as in the CCP9 and the solid state microscopy and spectroscopy communities at STFC Facilities. Workflow tools and coupling with the ChemShell QM/MM code will be developed to allow adoption of the code by the biomolecular simulations community. The code will also be ported to emerging supercomputing architectures with GPU accelerators.
Thus the project will support the rapidly-expanding communities within solid-state materials and biochemistry that deploy first-principles quantum simulations based on DFT. The project will deliver significant communication, engagement, and expert training and mentoring of new users to overcome initial barriers to access and enable them to use the code to make impact in their diverse research areas. Training events for both users and developers of the code will be embedded within each community.