  We devise a nonlocal correlation energy functional that describes the entire
range of dispersion interactions in a seamless fashion using only the electron
density as input. The new functional is considerably simpler than its
predecessors of a similar type. The functional has a tractable and robust
analytic form that lends itself to efficient self-consistent implementation.
When paired with an appropriate exchange functional, our nonlocal correlation
model yields accurate interaction energies of weakly-bound complexes, not only
near the energy minima but also far from equilibrium. Our model exhibits an
outstanding precision at predicting equilibrium intermonomer separations in van
der Waals complexes. It also gives accurate covalent bond lengths and
atomization energies. Hence the functional proposed in this work is a
computationally inexpensive electronic structure tool of broad applicability.
