Numerical (δx = 10–2 Å) and analytic anharmonic corrections to the spectral intensities both go in the same direction for each individual peak, but the magnitude of the corrections differs. The difference in the intensity of the anharmonic corrections to the infrared intensities between the numerical and analytic values varies from 10 to 230% of the analytic correction depending on the peak considered, with the majority of the corrections being in error by 35–85%, the only exceptions being the low-energy modes 81 and 91. However, there is no trend as to whether the numerical corrections under- or overestimate the analytic results. As the anharmonic corrections to the total intensity of the peaks is small, these differences are not easily visible from the spectra plotted in Fig. 2.