Thomas-fermi model electron density with correct boundary conditions: Applications to atoms and ions

We propose an electron density in atoms and ions, which has the Thomas-Ferm i-Dirac form in the intermediate region of r, satisfies the Kato condition for small r, and has the correct asymptotic behavior at large values of r, where r is the distance from the nucleus. We also analyze the perturbation in the density produced by multipolar fields. We use these densities in the Poisson equation to deduce average values of r(m), multipolar polarizabili ties, and dispersion coefficients of atoms and ions. The predictions are in good agreement with experimental and other theoretical values, generally w ithin about 20%. We tabulate here the coefficient A in the asymptotic densi ty; radial expectation values [r(m)] for m = 2, 4, 6; multipolar polarizabi lities alpha(1), alpha(2), alpha(3); expectation values [r(0)] and [r(2)] o f the asymptotic electron density; and the van der Waals coefficient C-6 fo r atoms and ions with 2 greater than or equal to Z greater than or equal to 92. Many of our results, particularly the multipolar polarizabilities and the higher order dispersion coefficients, are the only ones available in th e literature. The variation of these properties also provides interesting i nsight into the shell structure of atoms and ions. Overall, the Thomas-Ferr ni-Dirac model with the correct boundary conditions provides a good global description of atoms and ions. (C) 1999 Academic Press.