Abstract:
Total electronic energies are calculated numerically for
free and singly-ionized He, Li, C, and Ne atoms using density
functional theory. Immersion energies are calculated for a single
C impurity atom embedded or absorbed into a charge-neutral system
composed of a free-electron gas with uniform positive background,
also called 'jellium'. Nonspherical effects resulting from the
breaking of angular momentum symmetry are taken into account.
Previous work has been limited to spherical approximations to
these effects. Spin-polarization effects are incorporated through
the local spin-density approximation. Solving the resulting
coupled equations allows for a direct calculation of the total
energy and the dielectric response of the charge cloud to an
applied electric field.
For a free carbon atom, we show that the ground state
configuration predicted by the local spin density approximation
violates Hund's 2nd rule. For free He, C, and Ne atoms in the
presence of an applied electric field, we show that the
polarizabilities calculated directly are in good agreement with
previous results of perturbation theory and with experiment. For a
carbon impurity system, phase shifts of the free-electron states
are examined. Friedel oscillations and the Friedel sum rule are
used for physical verification of the solutions. In the limit of
low background density, we show that the impurity atom is affected
by the presence of the electron gas and does not necessarily
approach the free atom solution. Particularly, we show that the
orbital magnetic quantum number is quenched for a neutral C
impurity atom, even at very low background densities, which is
again in violation of Hund's 2nd rule. For a neutral carbon
impurity system, we show that the immersion energy changes from
negative to postive value as the orbital magnetic quantum number
is varied from 0-1.
