(456f) Molecular Modeling of Vapor-Deposited Ultra-Stable Glasses

Glasses are generally prepared by cooling from the liquid phase,
and their properties depend on the cooling rate. Computer
simulations of glass forming liquids have shed important insights
into the structure and properties of glasses, but the cooling rates
employed in past simulations have been many orders of magnitude
faster than those used in laboratory experiments. In this work we
present the formation of model glasses whose properties correspond
to those of a material prepared at a cooling rate that would be
more than nineteen orders of magnitude slower than previously
possible, thereby creating highly stable glasses whose energy is
the lowest ever achieved on a computer. Such glasses conceivably
represent the state that would be reached if one could age the
materials for thousands of years. Their properties are shown to
closely follow those of experimental vapor-deposited stable
glasses. Our findings will be discussed in the context of results
for binary Lennard-Jones glasses, trehalose glasses, and glycerol
glasses. In particular, in the case of vapor-deposited ultra-stable glasses, we find enhanced mechanical properties and slow-down of alpha relaxation processes as compared to ordinary glasses prepared by slow cooling of the liquid.