Libxc - a library of exchange and correlation functionals - TDDFT.org

Jacob’s ladder
Local density approximation:
E LDA
xc
(r) = Exc
LDA [n] ∣ n=n(r)
Generalized gradient approximation:
E GGA
xc
(r) = Exc
GGA [n, ∇n] ∣ n=n(r)
Meta-generalized gradient approximation:
E mGGA
xc
(r) = Exc
mGGA [n, ∇n, τ] ∣ n=n(r),τ=τ(r)
And more: orbital functionals, hybrid functionals, hyper-GGAs,
etc.
M. A. L. Marques Libxc