The Effect of Embedded Nanoparticles on the Phonon Spectrum of Ice: An Inelastic X-Ray Scattering Study

As a contribution to the ongoing effort toward high-frequency sound manipulation in composite materials, we use Inelastic X-Ray Scattering to probe the phonon spectrum of ice, either in pure form or with a sparse amount of nanoparticles embedded in it. The study aims at elucidating the ability of nanocolloids to condition collective atomic vibrations of the surrounding environment. We observe that a nanoparticle concentration of about 1 $\%$ in volume is sufficient to visibly affect the phonon spectrum of the icy substrate, mainly canceling its optical modes and adding to it nanoparticle phonon excitations. We highlight this phenomenon thanks to a lineshape modeling based on Bayesian inference, which enables us to capture the finest detail of the scattering signal. The results of this study can empower new routes toward the shaping of sound propagation in materials through the control of their structural heterogeneity.