  We numerically investigate the thermodynamic properties of the glass state.
As the object of our study, we employ a binary lattice gas model. Through Monte
Carlo simulations, we find that this model actually experiences a glass
transition. We introduce a potential into the model that represents a piston
with which we compress the glass. By measuring the work performed in this
process, we find that irreversible works exist at the glass state even in the
quasistatic limit. This implies that yield stress is created by the glass
transition.
