The CASSCF method: A perspective and commentary

Abstract The CASSCF method of Roos and coworkers is reviewed and compared to other approaches. It is argued that the implementation of the CASSCF method marks the beginning of large scale multiconfigurational self consistent field calculations and thus has been important in many fields of the molecular sciences. It is further argued that CASSCF and related approaches will continue to play an important role in the development of a molecular understanding of structures and processes in many fields of science, as these approaches constitute the appropriate starting point for wave function descriptions of molecules and complexes containing transition metals. This development will, however, require a way to avoid the exponential scaling of the complexity of the underlying wave function and several ways to eliminate this scaling is reviewed. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem 111:3267–3272, 2011