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HL: Fachverband Halbleiterphysik

HL 40: Impurities / Amorphous Semiconductors

HL 40.2: Talk

Tuesday, March 27, 2012, 11:45–12:00, EW 015

Vibrational spectra of charged point defects in ionic oxides — Jianchuan Wang, •Christoph Freysoldt, and Jörg Neugebauer — Max-Planck-Institut für Eisenforschung, Düsseldorf

We report calculations of the vibrational spectra of point defects which include the complete coupling to the host matrix. Such couplings are expected for charged defects in oxides and other ionic materials due to the long-range nature of electrostatic interactions. The dynamical matrix is computed from an electro-elastic model which combines long-range electrostatic forces with a pairwise interatomic harmonic correction for a limited number of neighbors. The model parameters are obtained from a few accurate density-functional theory ground-state calculations, requiring only forces and potentials which are readily available. Available symmetries are fully exploited. The approach is demonstrated for the +2 O vacancy in MgO. We show that the presence of the defect breaks the symmetry of the Born effective charge tensor of nearby atoms, and discuss the relevant sum rules. We also analyse how the defect modifies the vibrational density of states.