Weighted density approximation
In this approximation the Helmholtz energy function depends on the weighted density, that is: some average of the density.
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- J. A. Alonso and L. A. Girifalco "Nonlocal approximation to the exchange potential and kinetic energy of an inhomogeneous electron gas", Physical Review B '17 pp. 3735 - 3743 (1978)
- O. Gunnarsson, M. Jonson and B. I. Lundqvist "Descriptions of exchange and correlation effects in inhomogeneous electron systems" Physical Review B 20 3136 - 3164 (1979)