Computation of the expectation value of the spin operator ${\hat{S}}^2$ for the Spin-Flip Bethe-Salpeter Equation

Bradford A. Barker, Arabi Seshappan, David A. Strubbe

Spin-flip methods applied to excited-state approaches like the Bethe-Salpeter Equation allow access to the excitation energies of open-shell systems, such as molecules and defects…