  In modeling low-dimensional electronic nanostructures, the evaluation of the
electron-electron interaction is a challenging task. Here we present an
accurate and practical density-functional approach to the two-dimensional
many-electron problem. In particular, we show that spin-density functionals in
the class of meta-generalized-gradient approximations can be greatly simplified
by reducing the explicit dependence on the Kohn-Sham orbitals to the dependence
on the electron spin density and its spatial derivatives. Tests on various
quantum-dot systems show that the overall accuracy is well preserved, if not
even improved, by the modifications.
