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Manuscript Title: An RPA program for jellium spheres.
Authors: G. Bertsch
Program title: JELLYRPA
Catalogue identifier: ABTC_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 60(1990)247
Programming language: Fortran.
Computer: DIGITAL VAX 780.
Operating system: VAX/VMS.
RAM: 350K words
Word size: 8
Keywords: Random phase Approximation (rpa), Local density Approximation (lda), Jellium spheres, Polarization propagator, Radial transition Density, Strength function, Sum rules, Plasmon, Mie resonance, Scattering, Photon, Molecular physics.
Classification: 16.6.

Nature of problem:
The electromagnetic response of small metal particles and atomic clusters is an object of current experimental interest. The electric polarizability and the plasmon resonance are measured, among other properties. The quantum mechanical theory of the response in the many- electron system is still not fully developed, but the Random Phase Approximation (RPA) in the Local Density Approximation (LDA) is simple and accurate enough to serve as a theoretical baseline for more elaborate treatments. The program JELLYRPA computes the RPA/LDA response for small metal spheres, treating the atomic cores as a uniform positively charged background.

Solution method:
JELLYRPA uses the polarization propagator method in coordinate space to solve the equations for the response of the electrons to an external field. This method has the advantage that unbound excitations can be treated quite realistically, with the resonances automatically acquiring a width due to the ionization of the electrons. The method allows excitations to be calculated in very large spaces of configurations. The numerical difficulty in the evaluation of the polarization propagator is controlled by the mesh size in coordinate space, since the computation requires inversion of a matrix whose dimensionality is equal to the number of mesh points.

Restrictions:
The theory is best suited for closed shell systems where a Hartree-Fock or some effective mean field theory provides a good description of the ground state. Also, the polarization propagator method relies on a simple representation of the interaction, with very restricted possibilities for nonlocality. In particular, the exchange interaction can only be calculated approximately, in a zero range approximation. The interaction in the LDA is well suited to this method because exchange and correlation effects are approximated by a local function of density.

Running time:
250 s for input provided.