Conventional Density Functional Theory (DFT) calculations are limited to a few hundred atoms at most as the computational effort increases with the third power of the number of atoms. To overcome this severe limitation we have developed a unique reformulation of DFT with computational cost that increases only linearly, and allows calculations with thousands of atoms.
Localised orbitals are optimised in situ, and linear-scaling is achieved by taking advantage of the exponential decay of the density matrix according to the physical principle of “near-sightedness of electronic matter”.
However, on its own, the ability to do large-scale quantum calculations is still not enough to solve real problems of industrial relevance because molecules, biomolecules and nanoparticles are not isolated but interact strongly with each other and their environment (e.g. solvent) and are in constant thermal motion.
Therefore, this PhD will be focused towards developing new models with which to improve and augment our quantum chemistry simulations in order to achieve the required level of realism for the quantum system and its environment. These developments will be in the area of multiscale models which interface a high level of theory for the system of interest with a lower level of theory for its environment (e.g. solvent models, lower level quantum and classical theories, such as polarisable force fields). Further possible developments could include novel, more accurate DFT methods which connect with wavefunction-based methods or electronic response to external probes, as required in the simulation of various spectroscopies. The implementation of these highly non-trivial theories will need to be formulated within the localised wavefunction theoretical framework which is required for the linear-scaling computational effort. Modern software engineering principles will need to be used for these developments as they are intended for a high-quality parallel code with a large user and developer base.
The new methods that will be developed during this PhD will open the way for simulations with an unprecedented level of realism in grand-challenge applications such as the simulation of organic photovoltaic materials.
If you wish to discuss any details of the project informally, please contact Professor Chris-Kriton Skylaris, Email: [email protected], Tel: +44 (0) 2380 59 9381.