The intrinsic nature of glass states or glass transitions has been a mystery for a long time. Recently, more and more studies tend to show that a glass locates at a specific potential energy landscape (PEL). To explore how the flatness of the PEL related to glass transition, we develop a method to adjust the PEL in a controllable manner. We demonstrate that a relatively flat PEL is not only necessary but also sufficient for the formation of a nanoscale glass. We show that: (1) as long as a nanocluster is located in a region of PEL with local minimum deep enough, it can undergo a first-order solid-liquid phase transition; and (2) if a nanocluster is located in a relatively flat PEL, it can undergo a glass transition. All these transitions are independent of its structure symmetry, order or disorder. Our simulations also uncover the direct transition from one potential energy minimum to another below the glass transition temperature, which is the consequence of flat PELs.
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