Analytical State-Average Complete-Active-Space Self-Consistent Field Nonadiabatic Coupling Vectors: Implementation with Density-Fitted Two-Electron Integrals and Application to Conical Intersections.
Analytical state-average complete-active-space self-consistent field derivative (nonadiabatic) coupling vectors are implemented. Existing formulations are modified such that the implementation is compatible with Cholesky-based density fitting of two-electron integrals, which results in efficient calculations especially with large basis sets. Using analytical nonadiabatic coupling vectors, the optimization of conical intersections is implemented within the projected constrained optimization method. The standard description and characterization of conical intersections is reviewed and clarified, and a practical and unambiguous system for their classification and interpretation is put forward. These new tools are subsequently tested and benchmarked for 19 different conical intersections. The accuracy of the derivative coupling vectors is validated, and the information that can be drawn from the proposed characterization is discussed, demonstrating its usefulness.
Ignacio
I
Fdez Galván
Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.|Kenneth S. Pitzer Center for Theoretical Chemistry, Department of Chemistry, University of California , Berkeley, California 94720, United States.
Mickaël G
MG
Delcey
Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Oslo , P.O. Box 1033 Blindern, 0315 Oslo, Norway.
Thomas Bondo
TB
Pedersen
Dipartimento di Chimica "G. Ciamician", Università di Bologna , Via F. Selmi 2, IT-40126 Bologna, Italy.
Francesco
F
Aquilante
Roland
R
Lindh