Van der Waals Density Functional Theory with Applications

The details of a density functional that includes van der Waals (vdW) interactions are presented. In particular we give some key steps of the transition from a form for fully planar systems [Phys. Rev. B 62, 6997 (2000)] to a procedure for realistic layered compounds that have planar symmetry only on large distance scales, and which have strong covalent bonds within the layers. It is shown that the random-phase approximation of that original functional can be replaced by an approximation that is exact at large separation between vdW interacting fragments and seamless as the fragments merge. An approximation to the latter which renders the functional easily applicable and which preserves useful accuracy in both limits and in between is given. We report additional data from applications to forms of graphite, boron nitride, and molybdenum sulfide not reported in our previous communication [Phys. Rev. Lett. 91, 126402 (2003)].