The adsorptive properties of cyanide CN on coinage metal M Ž . electrodes M s Cu, Ag, Au have been investigated using a relativistic density functional method. The way to model the electrochemical potential applied to the electrodes is to consider the systems in the presence of a perturbative external field F. The fieldperturbative approach is proven to be a suitable method in interpreting the observed spectral shifts with electrode potential. The calculated potential-dependent shifts of and are similar for the three metals, in agreement with experiment M -CN C -M observations. The relativistic effects are required to account for the similarity in the frequency shifts of . The calculated vibrational tuning rates d rdF are M -CN C -N y7 y7 y7 y1 Ž . 6 . 61 = 10 , 6.61 = 10 , and 5.64 = 10 cm r Vrcm for M s Cu, Ag, and Au, respectively. The coupling of the M-CN and C-N internal modes contributes Ž . significantly about 25% to the size of the frequency shifts ⌬ of the ligand. The C -N effect of electric fields on the metal-CN y bonding is also investigated. It is shown that changes in the magnitude of CN y to the metal donation and M-CN bond strength occur under the influence of the electric field.