  The first principles density functional theory (DFT) is applied to study
effects of molecular adsorption on optical losses of silver (111) surface. The
ground states of the systems including water, methanol, and ethanol molecules
adsorbed on Ag (111) surface were obtained by the total energy minimization
method within the local density approximation (LDA). Optical functions were
calculated within the Random Phase Approximation (RPA) approach. Contribution
of the surface states to optical losses was studied by calculations of the
dielectric function of bare Ag (111) surface. Substantial modifications of the
real and imaginary parts of the dielectric functions spectra in the near
infrared and visible spectral regions, caused by surface states and molecular
adsorption, were obtained. The results are discussed in comparison with
available experimental data.
