In 2005, Silkin et al. described the so-called induced chargedensity (ICD) oscillations at Cu(111) surface within the linear response theory. They were caused by an external perturbing charge. The innovation here was to split the Cu electron structure into two parts: the 3D bulk electrons and s-pz surface state denoted as the 2D electron system. They found that in both electron system the charge density distribution decays as 1/r 2 , yet for the periodically time-varying potential they got they decay asymptotics of the form 1/r. Expressions for the charge density distributions are as below: