# Plotting theoretical infrared spectra

I recently had to plot some theoretical infrared spectra using the output of a DFT optimisation and frequency calculation performed in Gausian and didn’t want to have to plot everything in Gaussview. Here’s how to plot exactly the same spectrum as Gaussview, and hopefully a clear explanation of what Gaussian means by IR Intensities.
Here’s an example optimisation and frequency (opt+freq) calculation for CO2 using DFT (B3LYP XC Functional), and a reasonable basis set.