4.2. CT Diagnostics. The Λ metric (eq. 4) and the Γ metric (eq. 10) have often been used to detect errors in TD-DFT calculations. With few exceptions, it has been tacitly assumed that Λ should be evaluated in the CMO basis. The Γ metric was originally introduced with the same assumption, although in that case it was quickly realized that ∆r (and thus Γ) is sensitive to diffuse functions for Rydberg states. The use of NTOs was suggested as a means to mitigate that dependence, and results in Section 4 .1 explain why.