A density-functional model of the dispersion interaction

We have recently introduced [J. Chem. Phys. 122, 154104 (2005)] a simple parameter- free model of the dispersion interaction based on the instantaneous in space, dipole moment of the exchange hole. The model generates remarkably accurate interatomic and intermolecular C-6 dispersion coefficients, and geometries and binding energies of intermolecular complexes. The model involves, in its original form, occupied Hartree- Fock or Kohn- Sham orbitals. Here we present a density- functional reformulation depending only on total density, the gradient and Laplacian of the density, and the kinetic- energy density. This density- functional model performs as well as the explicitly orbital- dependent model, yet offers obvious computational advantages. (c) 2005 American Institute of Physics.