Theoretical analysis of the solid-state terahertz spectrum of the high explosive RDX

The solid-state terahertz (THz) spectrum (2–120 cm−1) of α-form cyclotrimethylenetrinitramine (RDX) has been simulated using solid-state density functional calculations at a BP/DNP level of theory. BP/DNP features are in good agreement with both 298 K and a new 7 K polycrystalline RDX THz spectrum. The 7 K RDX spectrum is noteworthy for several mode shifts and spectral detail that greatly aids mode assignments. Previous RDX isolated-molecule calculations (with six calculated modes below 125 cm−1) are incapable of accurately predicting the numerous features in this region, highlighting the importance of solid-state theoretical methods for solid-state terahertz feature assignments.