Local density functional for kinetic energy

One seeks a local functional of the electron density to give approximately the kinetic energy. The application is primarily to an otherwise uniform electron gas in the neighborhood of a defect or metal surface. The approach is through consideration of the charge distributions at a square potential step; $V_0\le E_F$ for a free surface and $V_0<E_F$ at an interface between two metals. The fit to the charge-density distributions for a linear potential appears equally satisfactory.