X-ray absorption spectra at the Pd K edge were obtained on as-quenched and annealed ${\mathrm{Pd}}_{76}$${\mathrm{B}}_{24}$ up to the onset of polymorphous crystallization. Nearest-neighbors extended x-ray-absorption fine-structure (EXAFS) data were compared with previously reported x-ray diffraction data. For the first time we show here that in metallic glasses the envelope changes of first-shell radial distribution function accounts for experimental EXAFS data. The chemical twinning model explains shorter- and medium-range order as detected by EXAFS and x-ray diffraction, both in amorphous and annealed states. We show that the structural reconstruction from the glass up to the establishment of long-range order is due to the increase in the correlation length l${̃}_a$, which represents the average spatial extent of correlated domains, within which the structural units (triangular prisms) maintain the same mutual orientation as in the crystal.

• Received 20 April 1987

DOI:https://doi.org/10.1103/PhysRevB.36.4734