Project Title: Computational study of the excitonics of doped organic molecular crystals for a room-temperature maser
Supervisors: Prof. Peter D. Haynes, Dr. Andrew Horsfield
Collaborators: Dr. Stuart Bogatko
Masers (microwave lasers) have long been restricted in their applications by the impracticality of their operating conditions. For instance, solid state masers require cryogenic freezing and strong magnetic fields. In 2012, the first room-temperature maser was demonstrated using a p-terphenyl crystal doped with pentacene . Before this can become a practical device, however, the lack of continuous operation must be dealt with, in addition to the efficiency of the maser.
This raises the question of whether replacing pentacene with other dopants can help to improve performance. An ab initio understanding of the excited states of pentacene would enable us to guide the work of experimentalists for maser development. This requires us to consider the impact that the p-terphenyl crystal environment has on these excitations. While wavefunction-based (WFT) quantum chemical methods can yield highly accurate results for excitation energies, their computational cost renders large systems such as this beyond their reach. Linear-scaling density functional theory (DFT), as implemented in the ONETEP software , can be used to efficiently simulate large systems, but DFT is a ground state theory at heart and thus unsuitable for excitonic properties.
My research will focus on combining these methods by considering a WFT subsystem to be embedded in a DFT environment . This will require the implementation of a link between ONETEP and a quantum chemical software package. Such an approach will enable us to treat the excited states with a high level of accuracy while providing a thorough description of the environment with which we can analyse the influence of the wider crystal.
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