Is there a Linear Term in the X-ray or Neutron Scattering in a Liquid Metal at Small Wave Number?

Abstract

We examine further, on theoretical grounds, whether a k term, in the small angle X-ray structure factor of liquid simple metals, has a well established theoretical basis. It is first pointed out that, whereas in the ion-ion structure factor it appears that the collective behaviour introduces a k term, in the electron-electron structure factor collective plasmon behaviour appears to wipe out the k term of the non-interacting Fermi hole. We also emphasize the need of small angle neutron scattering data to probe directly the phonon mode.