Recently, we have introduced a method based on geometric considerations, termed geometric direct minimization (GDM), to achieve robust convergence of self consistent field calculations. GDM was limited to calculations involving either spin-unrestricted orbitals or closed shell systems. We report the extension of the GDM method to treat open shell systems involving spin-restricted orbitals. Open shell systems pose a challenge for achieving robust convergence of the calculation. We compare the convergence using the GDM method to the convergence achieved by the well known direct inversion in the iterative space (DIIS) technique. This comparison demonstrates the ability of the GDM method to achieve robust convergence. Additionally we assess the importance of geometric considerations by comparing against an alternative direct minimization method that is not geometrically correct.
Convergence Analysis of Direct Minimization and Self-Consistent Iterations
