only. However, we rely on a formulation of the kinetic energy density that is derived from the Schrödinger equation, and so, dependent on the orbital components. This kinetic energy density is expressed in terms of orbital densities 𝜌 ! (𝒓), their gradients ∇𝜌 ! (𝒓), and the Laplacian of the total electron density ∇ 2 𝜌(𝒓):