We add an effective atom-centered nonlocal term to the exchange-correlation potential in order to cure the lack of London dispersion forces in std. d. functional theory. Calibration of this long-range correction is performed using d. functional perturbation theory and an arbitrary ref. Without any prior assignment of types and structures of mol. fragments, our cor. generalized gradient approxn. d. functional theory calcns. yield correct equil. geometries and dissocn. energies of argon-argon, benzene-benzene, graphite-graphite, and argon-benzene complexes. [on SciFinder (R)]