Exact Kohn-Sham versus Hartree-Fock in momentum space:Examples of two-fermion systems

摘要

The question of how density functional theory (DFT) compares with Hartree-Fock (HF) for the computation of momentum-space properties is addressed in relation to systems for which (near) exact Kohn-Sham (KS) and HF one-electron matrices are known.This makes it possible to objectively compare HF and exact KS and hence to assess the potential of DFT for momentum-space studies.The systems considered are the Moshinsky [Am.J.Phys.36,52 (1968)] atom,Hooke's atom,and light two-electron ions,for which expressions for correlated density matrices or momentum densities have been derived in closed form.The results obtained show that it is necessary to make a distinction between true and approximate DFTs.