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          Institute: MPI für bioanorganische Chemie     Collection: MPI für bioanorganische Chemie     Display Documents



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ID: 713296.0, MPI für bioanorganische Chemie / MPI für bioanorganische Chemie
Spin orbit coupling for molecular ab initio density matrix renormalization group calculations: Application to g-tensors
Authors:Römelt, Michael
Language:English
Date of Publication (YYYY-MM-DD):2015
Title of Journal:Journal of Chemical Physics
Journal Abbrev.:J. Phys. Chem.
Volume:143
Issue / Number:4
Start Page:044112-1
End Page:044112-8
Sequence Number of Article:044112
Review Status:Internal review
Audience:Experts Only
Abstract / Description:Spin Orbit Coupling (SOC) is introduced to molecular ab initio density matrix renormalization group (DMRG) calculations. In the presented scheme, one first approximates the electronic ground state and a number of excited states of the Born-Oppenheimer (BO) Hamiltonian with the aid of the DMRG algorithm. Owing to the spin-adaptation of the algorithm, the total spin S is a good quantum number for these states. After the non-relativistic DMRG calculation is finished, all magnetic sublevels of the calculated states are constructed explicitly, and the SOC operator is expanded in the resulting basis. To this end, spin orbit coupled energies and wavefunctions are obtained as eigenvalues and eigenfunctions of the full Hamiltonian matrix which is composed of the SOC operator matrix and the BO Hamiltonian matrix. This treatment corresponds to a quasi-degenerate perturbation theory approach and can be regarded as the molecular equivalent to atomic Russell-Saunders coupling. For the evaluation of SOC matrix elements, the full Breit-Pauli SOC Hamiltonian is approximated by the widely used spin-orbit mean field operator. This operator allows for an efficient use of the second quantized triplet replacement operators that are readily generated during the non-relativistic DMRG algorithm, together with the Wigner-Eckart theorem. With a set of spin-orbit coupled wavefunctions at hand, the molecular g-tensors are calculated following the scheme proposed by Gerloch and McMeeking. It interprets the effective molecular g-values as the slope of the energy difference between the lowest Kramers pair with respect to the strength of the applied magnetic field. Test calculations on a chemically relevant Mo complex demonstrate the capabilities of the presented method. (C) 2015 AIP Publishing LLC.
Comment of the Author/Creator:Date: 2015, JUL 28 2015
External Publication Status:published
Document Type:Article
Version Comment:Automatic journal name synchronization
Communicated by:N. N.
Affiliations:MPI für bioanorganische Chemie
Identifiers:ISI:000358929100018 [ID No:1]
ISSN:0021-9606 [ID No:2]
DOI:10.1063/1A927432 [ID No:3]
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