  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.
