Pressure-Induced Structural Relaxation in AmorphousPd40Ni40P20: The Formation Volume for Diffusion Defects

Structural relaxation induced by hydrostatic pressure is experimentally observed for the metallic glass ${\mathrm{Pd}}_{40}{\mathrm{Ni}}_{40}{\mathrm{P}}_{20}$. The pressure dependence of the structural state is displayed in the shape of the glass-transition peak that is measured by means of differential scanning calorimetry after annealing treatments at 563 K and pressures up to 0.75 GPa. Quantification of the effect using the free-volume theory yields a formation volume of $5.9\pm 0.5{Å}^3$ for defects in this glass. In combination with the previously determined pressure dependence for the Au diffusivity, a value of $5\pm 4{Å}^3$ is derived for the migration volume for Au diffusion.