The fully correlated frequency-independent Dirac–Coulomb–Breit Hamiltonian provides the most accurate description of electron–electron interaction before going to a genuine relativistic quantum electrodynamics theory of many-electron systems. In this work, we introduce a correlated Dirac–Coulomb–Breit multiconfigurational self-consistent-field method within the frameworks of complete active space and density matrix renormalization group. In this approach, the Dirac–Coulomb–Breit Hamiltonian is included variationally in both the mean-field and correlated electron treatment. We also analyze the importance of the Breit operator in electron correlation and the rotation between the positive- and negative-orbital space in the no-virtual-pair approximation. Atomic fine-structure splittings and lanthanide contraction in diatomic fluorides are used as benchmark studies to understand the contribution from the Breit correlation.
Correlated Dirac–Coulomb–Breit multiconfigurational self-consistent-field methods
Chad E. Hoyer, Lixin Lu, Hang Hu, Kirill D. Shumilov, Shichao Sun, Stefan Knecht, Xiaosong Li; Correlated Dirac–Coulomb–Breit multiconfigurational self-consistent-field methods. J. Chem. Phys. 28 January 2023; 158 (4): 044101. https://doi.org/10.1063/5.0133741
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