To explain the difference between SC and KP intensities, we analyzed the output from our static calculations and assigned the modes. The vibrations occurring at ≈ 3150 cm -1 correspond to the C-H stretches, which are isolated and barely affected by the changes in the overall lattice structure. The vibrational modes at ≈ 1600 cm -1 are collective motions involving the B-C and C-C stretching modes (Figure The reason for this observation is that the structure of layers 1 and 1', as well as the 2 and 2', are no longer identical for the snapshots from the SC trajectory. Hence, the collective motions in the layers are slightly different, which manifests in a broadening of the signal.