Liquid-like atoms in dense-packed solid glasses.

Revealing the microscopic structural and dynamic pictures of glasses is a long-standing challenge for scientists 1,2 . Extensive studies on the structure and relaxation dynamics of glasses have constructed the current classical picture 3-5 : glasses consist of some 'soft zones' of loosely bound atoms embedded in a tightly bound atomic matrix. Recent experiments have found an additional fast process in the relaxation spectra 6-9 , but the underlying physics of this process remains unclear. Here, combining extensive dynamic experiments and computer simulations, we reveal that this fast relaxation is associated with string-like diffusion of liquid-like atoms, which are inherited from the high-temperature liquids. Even at room temperature, some atoms in dense-packed metallic glasses can diffuse just as easily as they would in liquid states, with an experimentally determined viscosity as low as 10 7  Pa·s. This finding extends our current microscopic picture of glass solids and might help establish the dynamics-property relationship of glasses 4 .