The optical properties of ZnO nanowires containing defects are investigated using first-principles densityfunctional theory incorporating the LDA+ U formalism. Calculations include defects in the form of substitutional N, Zn, and O vacancies as well as +1 charged O vacancy. Our calculations reveal that the presence of vacancies contribute strongly to optical absorption in the visible. Furthermore, the presence of +1 charged O vacancy is found to result in a blueshift of the absorption peaks, reducing the number of wavelengths that can be absorbed in the visible. These findings can be a useful tool for the design of new generation of materials with improved solar radiation absorption.

Magnetic properties of various C60 polymers are calculated using tight-binding molecular-dynamics and ab initio methods. Our results suggest a mechanism involving an interplay between structural defects and sp(3) hybridization to be responsible for the origin of this magnetism. The onset of magnetism is found to occur much more readily for the Rh-C60 polymeric phase with defects than for any of the other polymers, in agreement with the recent experiment. Our estimate of the magnetic moment is also in very good agreement with the value observed in experiment.

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