Asymptotic Displaced Charge round Impurities in Metal Crystals with and without Surfaces

The response function F is expressed in terms of tbc Green function of the unperturbed system and attention is then focussed on two taxes: (i) A perfect periodic metal crystal, pert&d by V. (ii) A metal lattice with a surface in which V is embedded. A full discusxion is given of tbc inRucnce.of Fermi sutface topology on the anisotropy of Ap in the asymptotic n&m far from the defect. Provided V(r) has certain rcasonabk properties, it is shown that Ap r-‘x oscillatory function. For the bulk metal. I! can take values bctwc+zn I and 5 in ditTerent directions for Fermi surfaces with ~articulxr top&&. Pasribk expcrimcntx which hear on this anisotropy are briedy referred to. For a planar sutfrc. the displaced chm is sho&r range for V cmin the smface than fur the bulk metal, in most, but not all cases. For a chned Fermi surface with mn-zero curvature.. n = 5 for the paralkl con@uration.