Atomic-Spring-like Effect in Glassy Silica-Helium Composites

We determine the structural origin of an “atomic-spring-like effect” in a glassy silica-helium composite, which exhibits this mechanical property that reversibly accumulates and restores energy at the subnanoscale based on a high-pressure experimental pair distribution function study combined with atom-scale molecular simulations. These unexpected experimental results were obtained by using a 3 μm spot size 61 keV X-ray beam and large area detector and by subtracting the scattered intensity due to helium outside the sample from the silica signal at the same focal point for each pressure point. The compression behavior of the glassy silica-helium composite is characterized on a structural level by the change from a uni- to bimodal distribution in the inter-tetrahedral distances in the amorphous isotropic structure of silica. We propose a simple characterization of this atomic-spring-like glass property using impedance spectroscopy measurements.