Angularmomentum convergence of Korringa-Kohn-Rostoker Green's functionmethods

Abstract

The convergence of multiple-scattering-theory-based electronicstructure methods (e.g. the Korringa-Kohn-Rostoker (KKR) bandtheory method), is determined by lmax, the maximum value of theangular momentum quantum number l. It has been generally assumedthat lmax = 3 or 4 is sufficient to ensure a converged groundstate and other properties. Using the locally self-consistentmultiple-scattering method, which facilitates the use of very highvalues of lmax, it is shown that the convergence of KKR Green'sfunction methods is much slower than previously supposed, even whenspherical approximations to the crystal potential are used.Calculations for Cu using 3⩽lmax⩽16 indicate that thetotal energy is converged to within ~0.04 mRyd atlmax = 12. For both face-centred cubic and body-centred cubicstructures, the largest error in the total energy occurs atlmax = 4; lmax = 8 gives total energies, bulk moduli, andlattice constants that are converged to accuracies of 0.1 mRyd,0.1 Mbar, and 0.002 Bohr respectively.