Shell-structure-based functionals for the kinetic energy

A new group of shell-structure-based functionals, which rely on proper representation of the atomic shell structure in real space, is introduced. Starting from the model of a perfect piecewise exponential decaying electron density, an analytical expression for the kinetic energy density including two parameters is given. It is shown that parameter values which lead to a proper shell structure in real space give rise to suitable kinetic energy functionals.