In this case, these two effects almost cancel each other such that CTST agrees reasonably well with CVT/SCT. However, the CVT/SCT-M08-HX results with the standard scale factor are unsatisfactory. The issue lies again in the vibrational frequencies. Although M08-HX accurately predicts the classical barrier height, its standard scale factor leads to an overestimated barrier on the vibrationally adiabatic ground-state potential energy curve. This discrepancy is a known limitation of using standard scale factors at transition structures, and it is perhaps not surprising since the standard scale factors were determined for stable molecules that tend to have less anharmonicity than transition structures.