Van der Waals density functional: Self-consistent potential and the nature of the van der Waals bond

Abstract

We derive the exchange-correlation potential corresponding to the nonlocal\nvan der Waals density functional [M. Dion, H. Rydberg, E. Schroder, D. C.\nLangreth, and B. I. Lundqvist, Phys. Rev. Lett. 92, 246401 (2004)]. We use this\npotential for a self-consistent calculation of the ground state properties of a\nnumber of van der Waals complexes as well as crystalline silicon. For the\nlatter, where little or no van der Waals interaction is expected, we find that\nthe results are mostly determined by semilocal exchange and correlation as in\nstandard generalized gradient approximations (GGA), with the fully nonlocal\nterm giving little effect. On the other hand, our results for the van der Waals\ncomplexes show that the self-consistency has little effect at equilibrium\nseparations. This finding validates previous calculations with the same\nfunctional that treated the fully nonlocal term as a post GGA perturbation. A\ncomparison of our results with wave-function calculations demonstrates the\nusefulness of our approach. The exchange-correlation potential also allows us\nto calculate Hellmann-Feynman forces, hence providing the means for efficient\ngeometry relaxations as well as unleashing the potential use of other standard\ntechniques that depend on the self-consistent charge distribution. The nature\nof the van der Waals bond is discussed in terms of the self-consistent bonding\ncharge.\n

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Affiliated Institutions

• Chalmers University of Technology SE
• Rutgers, The State University of New Jersey US

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