A new form for the kinetic energy-density functional for many-electron systems

A new simple form for the atomic kinetic energy-density functional ( t ) is proposed as a sum of the Thomas-Fermi term and a radial correction term, namely, t [ p ] = (3/10) (3π 2 ) 2/3 p 5/3 - ( 1/40 )( r ·▽ p )/ r 2 , where the first term is the Thomas-Fermi term and p ( r ) is the Hartree-Fock atomic density. The correction term is part of the -(1/4)▽ 2 p term which occurs in the kinetic energy density; it adds mainly terms of O( Z 2 ) and O( Z 5/3 ) to the Z 7/3 atomic Thomas-Fermi energy. The above form generally displays improved local and global behaviour for atomic kinetic energies. Besides satisfying the virial theorem, it gives rise to chemical binding in molecules.