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; V₀≤EF for a free surface and V₀<EF at an interface between two metals. The fit to the charge-density distributions for a linear potential appears equally satisfactory.