  The isotropic chemical shifts can be calculated either by full-electron
configuration, or by hybrid functionals, which costs a large amount of
computational resources. To save the time, DFT+U could be employed to calculate
the isotropic chemical shifts. However, the calculated properties are very
sensitive to the Hubbard correction value $U_{eff}$. Here the double
Fermi-contact-shift verification approach with DFT+U method is proposed with
much higher computational efficiency, that is, simultaneously calculate the
Fermi-contact shifts on two nuclei ($^{6}Li$ and $^{17}O$) to predict the
optimal $U_{eff}$. The optimal $U_{eff}$ is also helpful to the calculations of
quadrupolar coupling constant $C_{Q}$, $g$-factor, band structure and density
of states.
