The first Hohenberg-Kohn theorem states that the external potential of a system is a unique functional of this quantity.
Meta-GGA approaches include the Laplacian of this quantity in addition to its gradient, and functions of it obtained using those approaches include M06 and TPSS. One definition of this quantity sets it equal to eight pi over three times Planck's constant cubed, all multiplied by the cube of the Fermi momentum. The total kinetic energy of a system is proportional to the integral of this quantity to the five-thirds power in the (*) Thomas- Fermi model. The LDA approximation assumes that the exchange and correlation energy depend only on the value of this quantity at each point in space. Hybrid functions of this quantity, such as B3LYP, can be obtained by including Hartree-Fock exchange. The first Hohenberg-Kohn theorem states that the external potential of a system is a unique functional of this quantity. For 10 points, name this quantity that is used instead of the wavefunction in DFT calculations to quantify the probability of finding an electron in a particular location.
Meta-GGA approaches include the Laplacian of this quantity in addition to its gradient, and functions of it obtained using those approaches include M06 and TPSS.
electron density [prompt on  density until "electron"]