Correlation energy, correlated electron density, and exchange-correlation potential in some spherically confined...

We report correlation energies, electron densities, and exchange-correlation potentials obtained from configuration interaction and density functional calculations on spherically confined He, Be, Be²⁺ , and Ne atoms. The variation of the correlation energy with the confinement radius R_c is relatively small for the He, Be²⁺ , and Ne systems. Curiously, the Lee-Yang-Parr (LYP) functional works well for weak confinements but fails completely for small R_c . However, in the neutral beryllium atom the CI correlation energy increases markedly with decreasing R_c . This effect is less pronounced at the density-functional theory level. The LYP functional performs very well for the unconfined Be atom, but fails badly for small R_c . The standard exchange-correlation potentials exhibit significant deviation from the "exact" potential obtained by inversion of Kohn-Sham equation. The LYP correlation potential behaves erratically at strong confinements. © 2016 Wiley Periodicals, Inc.