Calculation of zero-field splitting parameters by density functional theory and ab-initio methods
Final Report Abstract
In the framework of the first part of the project two major method development tasks were accomplished. A resolution of the identity approximation for spin-spin dipole integrals was developed and implemented into the quantum chemistry package ORCA. The approximated spin-spin integrals are available for the large-scale multi-reference configuration interaction treatment of the spin-spin coupling interaction. The second task was concerned with the development and implementation of a relativistic version of the state-averaged complete active state self-consistent field (SA-CASSCF) approach. The method follows the ‘ones-step procedure’ and treats spin-orbit coupling interaction on the same level as electron correlation. The program employs an intermediate coupling scheme which allows utilization of the complex configuration interaction coefficients, but real molecular orbitals. The orbital gradient was extended to account for a contribution from an effective oneelectron spin-orbit mean-field operator. Additional options to calculate g-tensors for Kramers systems and phosphorescence rates of organic molecules were programmed. The approach was implemented into the development branch of the ORCA program. In the second part of the project the performance of the implemented approaches was tested. Using approximated RI integrals the correlated calculations of ZFS parameters of a set of systems with 500MOs were completed. The performance of the widely used in EPR measurements point-dipole approximation was studied and limitations of this model was established.
Publications
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Interaction of Radical Pairs Through-Bond and Through-Space: Scope and Limitations of the Point-Dipole Approximation in Electron Paramagnetic Resonance Spectroscopy. J. Am. Chem. Soc., 2009. 131: p. 10092–10106
Riplinger, C., et al.
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The resolution of the identity approximation for calculations of spin-spin contribution to zero-field splitting parameters. J. Chem. Phys., 2010. 132: p. 144111-11
Ganyushin, D., et al.
