Abstract
Korringa-Kohn-Rostoker (KKR) Green's function, multiple-scattering theory is an ecient sitecentered,
electronic-structure technique for addressing an assembly of N scatterers. Wave-functions
are expanded in a spherical-wave basis on each scattering center and indexed up to a maximum
orbital and azimuthal number Lmax = (l;m)max, while scattering matrices, which determine spectral
properties, are truncated at Ltr = (l;m)tr where phase shifts l>ltr are negligible. Historically, Lmax
is set equal to Ltr, which is correct for large enough Lmax but not computationally expedient; a
better procedure retains higher-order (free-electron and single-site) contributions for Lmax > Ltr
with l>ltr set to zero [Zhang and Butler, Phys. Rev. B 46, 7433]. We present a numerically
ecient and accurate augmented-KKR Green's function formalism that solves the KKR equations
by exact matrix inversion [R3 process with rank N(ltr + 1)2] and includes higher-L contributions
via linear algebra [R2 process with rank N(lmax +1)2]. Augmented-KKR approach yields properly
normalized wave-functions, numerically cheaper basis-set convergence, and a total charge density
and electron count that agrees with Lloyd's formula. We apply our formalism to fcc Cu, bcc Fe
and L10 CoPt, and present the numerical results for accuracy and for the convergence of the total
energies, Fermi energies, and magnetic moments versus Lmax for a given Ltr.