Pseudotetrahedral organometallic complexes containing chromium(IV) and aryl ligands have been experimentally identified as promising molecular qubit candidates. Here we present a computational protocol based on multiconfiguration pair-density functional theory for computing singlet-triplet gaps and zero-field splitting (ZFS) parameters in Cr(IV) aryl complexes. We find that two multireference methods, multistate complete active space second-order perturbation theory (MS-CASPT2) and hybrid multistate pair-density functional theory (HMS-PDFT), perform better than Kohn-Sham density functional theory for singlet-triplet gaps. Despite the very small values of the ZFS parameters, both multireference methods performed qualitatively well. MS-CASPT2 and HMS-PDFT performed particularly well for predicting the trend in the ratio of the rhombic and axial ZFS parameters, |E/D|. We have also investigated the dependence and sensitivity of the calculated ZFS parameters on the active space and the molecular geometry. The methodologies outlined here can guide future prediction of ZFS parameters in molecular qubit candidates.
Bibliographical noteFunding Information:
We thank Prof. David Awschalom, Dr. Samuel Bayliss, and Pratiti Deb for helpful suggestions regarding the data analysis and Dr. Dihua Wu for contiunuing discussions of magnetic applications of PDFT. This material is based upon work supported by the U.S. Department of Energy Office of Science National Quantum Information Science Research Centers. The calculations performed in this study made use of the Research Computing Center (RCC) resources from the University of Chicago. The development of PDFT methods is supported in part by the Air Force Office of Scientific Research by Grant FA9550-20-1-0360.
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- Chromium(IV) aryl complexes
- Molecular qubits
- Multiconfigurational calculations
- Optically addressable qubits
- Singlet-triplet gap
- Zero-field splitting
PubMed: MeSH publication types
- Journal Article