Friedel Oscillation about a Friedel-Anderson Impurity
  The Friedel oscillations in the vicinity of a Friedel-Anderson (FA) impurity are investigated numerically. For an FA impurity in the local moment limit the normalized amplitude A({\xi}) is S-shaped, approximately zero at short distances, approaching two at large distances and crossing the value one at the characteristic length {\xi}_{1/2}. Surprisingly, the Friedel oscillations of a simple non-interacting Friedel impurity with a narrow resonance at the Fermi level show a very similar behavior of their amplitude A({\xi}). A comparison correlates the resonance width and the Kondo energy of the FA impurity with the characteristic length {\xi}_{1/2} of the Friedel oscillations. 
Yaqi Tao and Gerd Bergmann
cond-mat.str-el