Communication: Explicit construction of functional derivatives in potential-driven density-functional theory.
We propose a method for imposing an important exact constraint on model Kohn-Sham potentials, namely, the requirement that they be functional derivatives of functionals of the electron density ρ. In particular, we show that if a model potential v(r) involves no ingredients other than ρ, ∇ρ, and ∇(2)ρ, then the necessary and sufficient condition for v(r) to be a functional derivative is ∂v/∂∇ρ=∇(∂v/∂∇(2)ρ). Integrability conditions of this type can be used to construct functional derivatives without knowing their parent functionals. This opens up possibilities for developing model exchange-correlation potentials that do not lead to unphysical effects common to existing approximations. Application of the technique is illustrated with examples.
Gaiduk
Alex P
AP
Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada.
Staroverov
Viktor N
VN