Inelastic Neutron Scattering Study of Phonon Density of States of Iodine Oxides and First-Principles Calculations

Iodine oxides I₂O_y (y = 4, 5, 6) crystallize into atypical structures that fall between molecular- and framework-base types and exhibit high reactivity in an ambient environment, a property highly desired in the so-called “agent defeat materials”. Inelastic neutron scattering experiments were performed to determine the phonon density of states of the newly synthesized I₂O₅ and I₂O₆ samples. First-principles calculations were carried out for I₂O₄, I₂O₅, and I₂O₆ to predict their thermodynamic properties and phonon density of states. Comparison of the INS data with the Raman and infrared measurements as well as the first-principles calculations sheds light on their distinctive, anisotropic thermomechanical properties.