Excited States, Symmetry Breaking, and Unphysical Solutions in State-Specific CASSCF Theory.

ABSTRACT: State-specific electronic structure theory provides a route toward balanced excited-state wave functions by exploiting higher-energy stationary points of the electronic energy. Multiconfigurational wave function approximations can describe both closed- and open-shell excited states and avoid the issues associated with state-averaged approaches. We investigate the existence of higher-energy solutions in complete active space self-consistent field (CASSCF) theory and characterize their topological properties. We demonstrate that state-specific approximations can provide accurate higher-energy excited states in H₂ (6-31G) with more compact active spaces than would be required in a state-averaged formalism. We then elucidate the unphysical stationary points, demonstrating that they

SUBMITTER: Marie A 

PROVIDER: S-EPMC10226133 | biostudies-literature | 2023 May

REPOSITORIES: biostudies-literature