Lindhard and RPA susceptibility computations in extended momentum space   in electron doped cuprates
  We present an approximation for efficient calculation of the Lindhard susceptibility $\chi^{L}(q,\omega)$ in a periodic system through the use of simple products of real space functions and the fast Fourier transform (FFT). The method is illustrated by providing $\chi^{L}(q,\omega)$ results for the electron doped cuprate Nd$_{2-x}$Ce$_{x}$CuO$_{4}$ extended over several Brillouin zones. These results are relevant for interpreting inelastic X-ray scattering spectra from cuprates. 
Yung Jui Wang, B. Barbiellini, Hsin Lin, Tanmoy Das, Susmita Basak, P.   E. Mijnarends, S. Kaprzyk, R. S. Markiewicz and A. ...
cond-mat.str-el