A proposal of the approximate scheme for calculating the pair density

The density functional scheme for calculating the pair density is presented by means of the constrained-search technique. The resultant single-particle equation takes the form of a modified Hartree–Fock equation, which contains the kinetic contribution of the exchange-correlation energy functional as the correlation potential. A practical form of the kinetic contribution is also proposed with the aid of the scaling relations of the kinetic energy functionals.