Comparison of the convergence characteristics of some iterative wave function optimization methods

Abstract

The convergence properties of several iterative methods for the optimization of orbitals and configuration mixing coefficients in multiconfigurational electronic wave functions are compared. All of the iterative methods considered here are derived from corresponding approximate energy expressions. These energy expressions are discussed within the context of their suitability for the calculation of noninfinitesimal wave function corrections. A method based on the partitioned orbital Hessian matrix and which uses an approximate super‐CI secular equation for the wave function corrections is shown to posses second‐order convergence and to have the largest radius of convergence of the methods analyzed in detail in this work for several molecular examples. Particular attention is given to convergence properties for excited states, where the differences between these methods are most significant.