title: Shape of Multireference, Equation-of-Motion Coupled-Cluster, and Density Functional Theory Potential Energy Surfaces at a Conical Intersection.
abstract: We report and characterize ground-state and excited-state potential energy profiles using a variety of electronic structure methods along a loop lying on the branching plane associated with a conical intersection (CI) of a reduced retinal model, the penta-2,4-dieniminium cation (PSB3). Whereas the performance of the equation-of-motion coupled-cluster, density functional theory, and multireference methods had been tested along the excited- and ground-state paths of PSB3 in our earlier work, the ability of these methods to correctly describe the potential energy surface shape along a CI branching plane has not yet been investigated. This is the focus of the present contribution. We find, in agreement with earlier studies by others, that standard time-dependent DFT (TDDFT) does not yield the correct two-dimensional (i.e., conical) crossing along the branching plane but rather a one-dimensional (i.e., linear) crossing along the same plane. The same type of behavior is found for SS-CASPT2(IPEA=0), SS-CASPT2(IPEA=0.25), spin-projected SF-TDDFT, EOM-SF-CCSD, and, finally, for the reference MRCISD+Q method. In contrast, we found that MRCISD, CASSCF, MS-CASPT2(IPEA=0), MS-CASPT2(IPEA=0.25), XMCQDPT2, QD-NEVPT2, non-spin-projected SF-TDDFT, and SI-SA-REKS yield the expected conical crossing. To assess the effect of the different crossing topologies (i.e., linear or conical) on the PSB3 photoisomerization efficiency, we discuss the results of 100 semiclassical trajectories computed by CASSCF and SS-CASPT2(IPEA=0.25) for a PSB3 derivative. We show that for the same initial conditions, the two methods yield similar dynamics leading to isomerization quantum yields that differ by only a few percent.
authors.affiliation: Department of Chemistry, Bowling Green State University , Bowling Green, Ohio 43403, United States.
authors.forename: Samer
authors.initials: S
authors.lastname: Gozem
authors.affiliation: Dipartimento di Biotecnologie, Chimica e Farmacia, Università di Siena , via A. Moro 2, I-53100 Siena, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Melaccio
authors.affiliation: Dipartimento di Biotecnologie, Chimica e Farmacia, Università di Siena , via A. Moro 2, I-53100 Siena, Italy.|Departamento de Química Física, Universidad de Alcalá , E-28871 Alcalá de Henares, Madrid, Spain.
authors.forename: Alessio
authors.initials: A
authors.lastname: Valentini
authors.affiliation: Institut für Physikalische und Theoretische Chemie, Universität Bonn , Beringstrasse 4, 53115 Bonn, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Filatov
authors.affiliation: Aix-Marseille Université, CNRS, Institut de Chimie Radicalaire , Marseille, France.
authors.forename: Miquel
authors.initials: M
authors.lastname: Huix-Rotllant
authors.affiliation: Aix-Marseille Université, CNRS, Institut de Chimie Radicalaire , Marseille, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Ferré
authors.affiliation: Departamento de Química Física, Universidad de Alcalá , E-28871 Alcalá de Henares, Madrid, Spain.
authors.forename: Luis Manuel
authors.initials: LM
authors.lastname: Frutos
authors.affiliation: Dipartimento di Scienze Chimiche e Farmaceutiche, Università di Ferrara , via Fossato di Mortara 17, I-44121 Ferrara, Italy.
authors.forename: Celestino
authors.initials: C
authors.lastname: Angeli
authors.affiliation: Department of Chemistry, University of Southern California , Los Angeles, California 90089-0482, United States.
authors.forename: Anna I
authors.initials: AI
authors.lastname: Krylov
authors.affiliation: Firefly Project, Moscow 117593, Russia.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Granovsky
authors.affiliation: Department of Chemistry - Ångström, the Theoretical Chemistry Programme, POB 518, SE-751 20 Uppsala, Sweden.
authors.forename: Roland
authors.initials: R
authors.lastname: Lindh
authors.affiliation: Department of Chemistry, Bowling Green State University , Bowling Green, Ohio 43403, United States.|Dipartimento di Biotecnologie, Chimica e Farmacia, Università di Siena , via A. Moro 2, I-53100 Siena, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Olivucci