CHARGE SUSCEPTIBILITY AND CHARGE CORRELATION-FUNCTION IN THE D-P MODEL

The properties of the charge fluctuation are investigated in the d-p m odel with the repulsion U-pd between holes on the nearest-neighbor Cu and O sites and the infinite on-site repulsion U-d at the Cu site. We calculate the charge susceptibility chi(c)(q, i omega(n)) and the char ge correlation function S-c(q)=T Sigma(omega n)chi(c)(q, i omega(n)). It is found that S-c(q) has a peak at the Gamma point and a maximum in a ring around the Gamma point. The former is due to T chi(c)(q, 0). I ts intensity is proportional to temperature T and strongly enhanced by U-pd. The latter is due to T Sigma(omega n not equal 0)chi(c)(q, i om ega(n)) and shows a weak T and U-pd dependence. The intensity of the d iffuse X-ray scattering on taking the charge fluctuation into account is also calculated. The result is consistent with the experiments in L a2-deltaSrdeltaCuO4.