2022-01-312022-01-312018https://repository.tcu.edu/handle/116099117/49934Parameter-free atomistic simulations of entangled solid-state paramagnetic defects may aid in the rational design of devices for quantum information science. This work applies time-dependent density functional theory (TDDFT) embedded-cluster simulations to a prototype entangled-defect system, namely two adjacent singlet-coupled F color centers in lithium fluoride. TDDFT calculations accurately reproduce the experimental visible absorption of both isolated and coupled F centers. The most accurate results are obtained by combining spin symmetry breaking to simulate strong correlation, a large fraction of exact (Hartree-Fock-like) exchange to minimize the defect electrons' self-interaction error, and a standard semilocal approximation for dynamical correlations between the defect electrons and the surrounding ionic lattice. These results motivate application of two-reference correlated ab initio approximations to the M-center, and application of TDDFT in parameter-free simulations of more complex entangled paramagnetic defect architectures.enGeneralized Gradient ApproximationHartree-FockF-CenterExcitation-EnergiesCircular-DichroismSpin QubitsExchangeRangeStatesThermochemistryArticleJournal license permits posting of VOR in repository.https://doi.org/10.1103/PhysRevB.97.085138