Electron-Hole and Plasmon Excitations in 3d Transition Metals: Ab Initio Calculations and Inelastic X-ray Scattering Measurements

We report extensive all-electron time-dependent density-functional calculations and nonresonant inelastic x-ray scattering measurements of the dynamical structure factor of 3d transition metals. For small wave vectors, a plasmon peak is observed which is well described by our calculations. At large wave vectors, both theory and experiment exhibit characteristic low-energy electron-hole excitations of d character which correlate with the presence of d bands below and above the Fermi level. Our calculations, which have been carried out in the random-phase and adiabatic local-density approximations, are found to be in remarkable agreement with the measured dynamical structure factors of Sc and Cr at energies below the semicore onset energy (M edge) of these materials.