The performance of the strongly constrained and appropriately normed (SCAN) [Phys. Rev. Lett.
115, 036402 (2015)] meta-generalised gradient approximation exchange–correlation functional is
investigated for the calculation of time-dependent density-functional theory (TDDFT) molecular
excitation energies of local, charge-transfer, and Rydberg character, together with the excited 3Σ+u potential energy curve in H2. The SCAN results frequently resemble those obtained using a global hybrid functional, with either a standard or increased fraction of exact orbital exchange. For
local excitations, SCAN can exhibit significant triplet instability problems, resulting in imaginary
triplet excitation energies for a number of cases. The Tamm–Dancoff approximation offers a simple approach to improve the situation, but the excitation energies are still significantly underestimated.
Understanding the origin of these (near)-triplet instabilities may provide useful insight into future
functional development.