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Charge state dependent Jahn-Teller distortions of the e-center defect in crystalline Si.

The atomic and electronic structures of a lattice vacancy trapped next to an As impurity (the E-center defect) in crystalline Si are investigated using ab initio pseudopotential total energy calculations. Jahn-Teller distortions and energies, reorientation barriers, defect wave function characters, and hyperfine coupling parameters associated with (-) and (0) charge states of the E center are calculated using a combination of real-space cluster and plane wave supercell methods. For the first time in the theoretical study of this defect, the senses of the Jahn-Teller distortions in the two charge states are found to be opposite, changing from a large pairing type in (0) to a large resonant-bond type distortion in the (-) charge state, in agreement with experimental data.