Exchange-correlation energy functionals for electrons in two dimensions.

Two-dimensional (2D) electronic systems have attracted vast interest in condense matter physics since the beginning of semiconductor technology. Density-functional theory (DFT) is among the available theoretical and computational methods to deal with many-electron systems. Fundamental quantity in DFT is the exchange-correlation (xc) energy functional. In practice, this functional needs to be approximated. Many approximations have been developed for three-dimensional (3D) systems that, unfortunately, are inadequate for 2D systems. Hence, there is a clear need for new approximations specifically designed for 2D systems. Following this important need, efficient and practical expressions for the xc-energy of electrons in 2D are presented. Numerical results for finite systems show that the proposed functionals outperform the standard 2D local-spin-density approximation.