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DEFECT - AB INITIO RANDOM STRUCTURE SEARCHING The search for point-defects The new single Si, single H, defect in bulk silicon. One of the many new structures discovered using the method.

"One of the continuing scandals in the physical sciences is that it remains in general impossible to predict the structure of even the simplest crystalline solids from a knowledge of their chemical composition." J. Maddox Nature 335 201 (1988) Collaborators: Chris Pickard Richard Needs Dorothy Duffy Jack Mulroue Clare P. Grey

We use computational Quantum Mechanics, within the density-functional theory framework to predict the ground-state structures of solids. The method simply minimises the forces on a set of random atom starting positions. This procedure is repeated many times with different starting configurations. This produces a set of relaxed structures, the lowest energy of which, we take as the ground state.

Over the past few months I have been modifying the method to be able to study defects in semiconductors. This is an important problem, as defects in bulk semiconductors can drastically alter the electronic properties of the semiconductor

PUBLICATIONS

1. Energetics of hydrogen/lithium complexes in silicon analyzed using the Maxwell construction A. J. Morris, C. P. Grey, R. J. Needs and C. J. Pickard [Phys. Rev. B 84, 224106 (2011)][arχiv]
2. Ab initio study of intrinsic defects in zirconolite Jack Mulroue, Andrew J. Morris and Dorothy M. Duffy, [Phys. Rev. B 84, 094118 (2011)] [arχiv]
3. Hydrogen/nitrogen/oxygen complexes in silicon from computational searches Andrew. J. Morris, Chris J. Pickard and R. J. Needs. [Phys. Rev. B 80, 144112 (2009)] [arχiv]
4. Hydrogen/silicon complexes in silicon from computational searches Andrew. J. Morris, Chris J. Pickard and R. J. Needs. [Phys. Rev. B 78, 184102 (2008)] [arχiv]