Development of Kinetic Energy Density Functional Using Response Function
Defined on the Energy Coordinate
Abstract
A kinetic energy functional Ee was developed within the framework of the
density-functional theory (DFT) based on the energy electron density for
the purpose of realizing the orbital-free DFT. The functional includes
the nonlocal term described with the linear-response function (LRF) of a
reference system. As a notable feature of the present approach, the LRF
is represented on the energy coordinate ε defined for each system of
interest. In addition, an atomic system is taken as a reference system
for the construction of the LRF, which shows a clear difference from the
conventional approach based on the homogeneous electron gas. The
explicit form of the functional Ee was formulated by means of the
coupling-parameter integration scheme. The functional Ee was applied to
the calculations of the kinetic energies of the pseudo atoms that mimics
H, He, Ne, and Ar. Explicitly, the kinetic energy of each atom was
computed using the functional Ee with respect to the variation of the
valence charge Zv of each atom. In these calculations, the electron
density n optimized by the Kohn-Sham DFT was adopted as an argument of
the functional. It was found that the results are in excellent
agreements with those given by the Kohn-Sham DFT. We also devised a
method to perform the self-consistent field calculation utilizing the
functional Ee The method was applied to the computation of the radial
distribution functions of the electrons in the pseudo Ne and Ar atoms.
It was demonstrated that the results reasonably agree with those yielded
by the Kohn-Sham DFT.