  When a liquid melt is cooled, a glass or phase transition can be obtained
depending on the cooling rate. Yet, this behavior has not been clearly captured
in energy landscape models. Here a model is provided in which two key
ingredients are considered based in the landscape, metastable states and their
multiplicity. Metastable states are considered as in two level system models.
However, their multiplicity and topology allows a phase transition in the
thermodynamic limit, while a transition to the glass is obtained for fast
cooling. By solving the corresponding master equation, the minimal speed of
cooling required to produce the glass is obtained as a function of the
distribution of metastable and stable states. This allows to understand cooling
trends due to rigidity considerations in chalcogenide glasses.
