Relativistic central-field Green's functions for the Ratip package

Unusual features of the program:Xgreens has been designed as a part of the Ratip package [S. Fritzsche, J. Elec. Spec. Rel. Phen. 114-116 (2001) 1155] for the calculation of relativistic atomic transition and ionization properties. In a short dialog at the beginning of the execution, the user can specify the choice of the potential as well as the energies and the symmetries of the radial Green's functions to be calculated. Apart from central-field Green's functions, of course, the Coulomb Green's function [P. Koval, S. Fritzsche, Comput. Phys. Comm. 152 (2003) 191] can also be computed by selecting a constant nuclear charge Z(r)=Zeff. In order to test the generated Green's functions, moreover, we compare the two lowest bound-state orbitals which are calculated from the Green's functions with those as generated separately for the given potential. Like the other components of the Ratip package, Xgreens makes careful use of the Fortran 90/95 standard.