Hexamethylene triperoxide diamine (HMTD) is a powerful initiating explosive belonging to the family of triperoxide energetic materials. Single-crystal X-ray studies of this compound have revealed exactly planar 3-fold coordination about the two bridgehead nitrogen atoms. We have performed density functional theory B3LYP/6-31+G(d) calculations of HMTD to study the electronic nature of this very unusual coordination and to analyze the energetics and structure of this high-energy compound. The calculated geometry of HMTD was found to agree very well with the X-ray data. The vibrational spectrum of this molecule was also calculated and favorably compared to a diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) single-crystal spectrum.