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Photonic crystal modelling
David Bird graduated from the University of Cambridge in 1979 and stayed in Cambridge to study for his PhD in the Theory of Condensed Matter group at the Cavendish Laboratory. After holding a post-doctoral fellowship at the University of Bristol, he moved to Bath in 1984. He became a professor in 1995 and leader of the Physics department's condensed matter theory group in 1999.
He has made several key contributions in the development and application of large-scale, first-principles electronic structure calculations, based on density functional theory (DFT) and using plane-wave pseudopotential methods. For example, he developed a highly efficient computational method to include gradient corrections to the exchange-correlation potential. This is now used in virtually all grid-based DFT codes throughout the world. He has also pioneered the use of large-scale DFT calculations in studying molecular adsorption and dissociation at surfaces. Recent work in this field has focussed on the extension of standard DFT methods to include non-adiabatic effects at surfaces.
For the past three years he has also worked on developing efficient methods for the computational solution of Maxwell's equations in structured dielectrics, with a particular emphasis on photonic crystal fibres. The ideas are based on the DFT plane-wave methods mentioned above, but there are new and difficult challenges posed by the vector nature of the equation (the operator for a fixed-frequency method is non-Hermitian) and the requirement to compute eigenvalues in the interior of the spectrum (needed for the most important modes in hollow-core PCF). The code we have developed at Bath is highly efficient and is being used in the CPPM for a wide range of PCF structures. Work is continuing on further improvements in speed and memory efficiency, and on the application of the novel computational methods to other classes of photonic crystals.