Dispersion interactions from a local polarizability model

A local approximation for dynamic polarizability leads to a nonlocal functional for the long-range dispersion interaction energy via an imaginary-frequency integral. We analyze several local polarizability approximations and argue that the form underlying the construction of our recent van der Waals functional [O. A. Vydrov and T. Van Voorhis, Phys. Rev. Lett. 103, 063004 (2009)] is particularly well physically justified. Using this improved formula, we compute dynamic dipole polarizabilities and van der Waals $C_6$ coefficients for a set of atoms and molecules. Good agreement with the benchmark values is obtained in most cases.

Figure 1

Average dynamic dipole polarizabilities at imaginary frequencies calculated using the VV09 model [i.e., via Eqs. (2) and (13)]. Atomic units are used. The reference values are from Ref. [39] for LiH and from Ref. [40] for the atoms.