Cubic contributions in multiconfigurational self-consistent-field (MCSCF) calculations

Abstract
We discuss implementation of cubic contributions in multiconfigurational self‐consistent field (MCSCF) calculations. We explicitly demonstrate that, far from convergence, an iterative cubic technique can often eliminate the need for constraint procedures. Chebyshev (perturbative) and recursive (two‐point fixed Hessian) cubic techniques are shown to be useful for local, but not global convergence.