DFT calculations have been performed using RB3LYP with LANL3DZ basis sets to investigate the nature of the surface complex formed on the silver nanoparticles in aqueous medium (pH~9) in the presence of benzotriazole. For the above system geometry optimizations were performed in aqueous solution applying CPCM (COSMO) dielectric continuum model. The favourable interaction of the frontier orbitals localized on Ag⁺ and negatively charged nitrogen from the triazole ring leads to the formation of the stable (up to 120 kJ mol^-1) charge transfer complex. Raman active harmonic frequency calculations were done for the various surface complex models and compared with the experimental frequency values. Based on this, the most reliable structure was determined. The feasibility of the formation of the polymeric species has also been discussed.