Organization of Coordination Polyhedra in an Amorphous Binary Alloy

The local and intermediate structure of a simulated metal−metalloid glass-forming alloy is reported. The model, due to Kob and Andersen, has been the subject of considerable study in the context of the glass transition. In the A 75 B 25 mixture the low-temperature coordination polyhedra about the B (“metalloid”) particles are dominated by geometries based on either the capped trigonal prism or the square antiprism. As the concentration of B particles increases from 0.25 to 0.5, the B coordination changes from regular 8- and 9-fold polyhedra to distorted and irregular 6- and 7-fold geometries.