Change of Compressiblity at the Glass Transition and Prigogine-Defay Ratio in ZrTiCuNiBe Alloys

The change of the compressibility at the glass transition $T_g$ is evaluated from pressure experiments in the liquid and the glassy state of the ZrTiCuNiBe bulk metallic glass forming system. Via the enthalpy recovery method, we derive an increase of $T_g$ with pressure of $3.6\mathrm{K}/\mathrm{GPa}$. Comparing the changes of the compressibility, the specific heat capacity, and the thermal expansion coefficient at $T_g$, we estimate for the first time a Prigogine-Defay ratio in metallic systems. This ratio is about 2.4 for the present alloy and compares well with known nonmetallic glass forming systems.