New exchange-correlation density functionals: The role of the kinetic-energy density

New density functionals, using the kinetic-energy density Tau are reported. The newly introduced variable enhances the performance of previous functionals, leading to highly accurate functionals with and without the use of exact exchange. All these functionals are compared to commonly used functionals for a large test set, looking also at reactions and hydrogen bonded systems. Furthermore, their physical plausibility is discussed. (C) 2002 American Institute of Physics.