First-principles molecular-dynamics simulations are used to predict the structures and binding energies of interstitial nitrogen ${\mathrm{N}}_{\mathrm{i}},$ substitutional nitrogen ${\mathrm{N}}_{\mathrm{s}},$ the ${\mathrm{N}}_{\mathrm{i}}$-self-interstitial complex, the $\{{\mathrm{N}}_{\mathrm{i}},{\mathrm{N}}_{\mathrm{i}}\},$ $\{{\mathrm{N}}_{\mathrm{i}},{\mathrm{N}}_{\mathrm{s}}\}=\{{\mathrm{N}}_2,\mathrm{V}\},$ and $\{{\mathrm{N}}_{\mathrm{s}},{\mathrm{N}}_{\mathrm{s}}\}=\{{\mathrm{N}}_2,{\mathrm{V}}_2\}$ pairs (V is the vacancy). The interactions of N with H in Si are studied and the properties of several $\{\mathrm{N},\mathrm{H}\}$ complexes are predicted. The dynamical matrices yield many new local and pseudolocal vibrational modes associated with the impurities and their Si nearest neighbors. The unidentified $\{\mathrm{N},\mathrm{H}\}$-related infrared absorption line reported by Pajot et al. is assigned to the $\{{\mathrm{N}}_{\mathrm{s}},\mathrm{H}\}$ complex.

• Received 4 June 2003

DOI:https://doi.org/10.1103/PhysRevB.69.165206