Hydrogen pairs and local vibrational frequencies in H-irradiated GaAs1-yNy -: art. no. 073202

First-principles total energy calculations show that proton relaxation in H-irradiated GaAs1-yNy follows an energy pathway to form a charged dihydride, instead of the charge-neutral H-2* monohydride. Charge neutralization will take place later, as the sample is grounded, which will lead to the spontaneous canting of the dihydrides. This canted N-2H model explains the recent puzzling IR observation, the recoveries of the GaAs band gap and lattice parameter, and the dihydride symmetry determined by the x-ray absorption near-edge structure experiment. It may also have broad implications for ion implantation studies in other solids.