Terahertz optical properties of the high explosive -HMX

We have calculated the full dielectric function in the far-infrared for the high explosive β -HMX using density functional perturbation theory. Complementary time-domain terahertz spectroscopy measurements were performed on military-grade samples of HMX. The calculated absorption coefficient in the range 0.1–3.6 THz is in excellent quantitative agreement with our experimentally determined absorption coefficient in terms of both peak positions and magnitude. Our calculated refractive index below 1 THz is 1.68, very close to our measured value of 1.71. This computational method appears well suited for first-principles calculation of the terahertz optical properties of molecular crystals.