where C is the unitary transformation matrix between the TD and bare harmonic eigenvectors. Eq. 13 can be directly applied even for imaginary ω λq,h . Eqs. 12 and 13 are identical when C = I and ω λq (T ) = |ω λq,h |, and Eq. 13 tends to one-half of Eq. 12 as ω λq (T ) increases. Refer to Figure for a graphical comparison. Both corrections are implemented in the workflow, but the free energy results shown in this paper use Eq. 13.