Abstract
Amorphous materials are structurally complex compounds, some of which exhibit network glass topologies, with ongoing fundamental questions on their local 1,2 /intermediate 3,4 orders, transitions between 'polyamorphs' 5,6 or in the liquid state 7,8. These features, which are responsible for interesting physical properties, are widely used in optical and electronic devices as found in the special case of the archetype amorphous silica, a-silica. Here we determine the structural origin of an "atomic-spring effect" in an amorphous silica-helium composite, which exhibits a mechanical property that reversibly accumulates and restores energy at the subnanoscale. Such an "atomic-spring mechanical