High energy materials find use in many important technological applications ranging from batteries, to new fuels, to explosives. Due to their nature, these materials tend to have a high tendency to decompose and thus their long term storage and preservation poses significant challenges.
The goal of this project is to use and further develop atomistic simulation methods to understand at the atomic level the mechanisms that lead to decomposition of such materials and how these vary under different external conditions and chemical additives. For example, nitrocellulose (NC) is a high energy polymeric material which degrades by a number of different chemical processes over time. The rates of these processes depend upon the material’s particular environmental conditions. At temperatures between 100 °C and 200 °C it undergoes thermolysis at the nitrate ester groups releasing NO2. At lower temperatures, and in the presence of water, it undergoes hydrolysis to again yield NO2. The NO2 released then reacts within the binder materials generating reduced products such as NO and N2O which have been observed experimentally. However, the precise reactions which take place, how these might depend upon local conditions (such as the presence of water), and their rates (allowing for an estimation of the amount of product generated in a given time), are currently not well understood. Such problems are inherently multiscale and a hierarchy of methods need to be used to tackle the different length-scales and time-scales involved. For example, dynamics simulations with classical force fields will be used to explore the conformational space that the polymer chains can reach. At the same time, to simulate chemical reactions we will need to use methods such as first principles quantum mechanical calculations that explicitly describe the electronic rearrangements in molecules.
Conventional quantum approaches are typically limited to simulations with no more than a few tens of atoms, as the computational effort scales with the third power in the number of atoms in the simulation. However, the modelling of complex polymeric materials will require simulations with up to several thousand atoms. To achieve this we propose to use the linear-scaling DFT program ONETEP which we develop in our group and is able to perform quantum calculations with thousands of atoms. Particular challenges in this project will be the identification of possible reactions and the development of approaches to follow particular reaction paths.
The project will be supervised by Professor Chris-Kriton Skylaris at the University of Southampton and by industrial collaborators.
This project is open only to applicants who are UK nationals.
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.