Title: Discovery of a paired Gaussian and long-tailed distribution of potential energies in nanoglasses

Abstract: It is generally believed that the intrinsic properties of glasses are intimately related to potential-energy landscapes (PELs). However, little is known about the PELs of glasses below the glass transition temperature (Tg). Taking advantage of lower potential-energy barriers in nanosystems, we have systematically investigated the dynamics behavior of two nanoglasses, Al43 and Al46. Structure transformation is identified in our pure molecular-dynamics simulation far below Tg, which manifests the existence of metabasins in PELs, at least for nanoglasses. Surprisingly, we find that the distribution of potential energies shows a paired Gaussian and long-tailed distribution at temperatures below and approaching Tg; correspondingly, the distribution of the {\alpha}-relaxation time exhibits an exponential-like decay. In contrast to the Gaussian distribution of energy in typical liquids and solids, the unexpected distribution may reflect the intrinsic feature of nanoglasses. Associated with the exponential-like distribution of the {\alpha}-relaxation time, the stretched-exponential structural relaxation is found, and the maximum stretched behavior appears around Tg. Despite our studies focused on nanoglasses, the current finding may shed light on future studies of bulk glasses.