title: Communication: DMRG-SCF study of the singlet, triplet, and quintet states of oxo-Mn(Salen).
abstract: We use CheMPS2, our free open-source spin-adapted implementation of the density matrix renormalization group (DMRG) [S. Wouters, W. Poelmans, P. W. Ayers, and D. Van Neck, Comput. Phys. Commun. 185, 1501 (2014)], to study the lowest singlet, triplet, and quintet states of the oxo-Mn(Salen) complex. We describe how an initial approximate DMRG calculation in a large active space around the Fermi level can be used to obtain a good set of starting orbitals for subsequent complete-active-space or DMRG self-consistent field calculations. This procedure mitigates the need for a localization procedure, followed by a manual selection of the active space. Per multiplicity, the same active space of 28 electrons in 22 orbitals (28e, 22o) is obtained with the 6-31G(*), cc-pVDZ, and ANO-RCC-VDZP basis sets (the latter with DKH2 scalar relativistic corrections). Our calculations provide new insight into the electronic structure of the quintet.
authors.affiliation: Center for Molecular Modelling, Ghent University, Technologiepark 903, 9052 Zwijnaarde, Belgium.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Wouters
authors.affiliation: Center for Molecular Modelling, Ghent University, Technologiepark 903, 9052 Zwijnaarde, Belgium.
authors.forename: Thomas
authors.initials: T
authors.lastname: Bogaerts
authors.affiliation: Center for Ordered Materials, Organometallics and Catalysis, Ghent University, Krijgslaan 281 (S3), 9000 Gent, Belgium.
authors.forename: Pascal
authors.initials: P
authors.lastname: Van Der Voort
authors.affiliation: Center for Molecular Modelling, Ghent University, Technologiepark 903, 9052 Zwijnaarde, Belgium.
authors.forename: Veronique
authors.initials: V
authors.lastname: Van Speybroeck
authors.affiliation: Center for Molecular Modelling, Ghent University, Technologiepark 903, 9052 Zwijnaarde, Belgium.
authors.forename: Dimitri
authors.initials: D
authors.lastname: Van Neck