The effects of Si substitution on the glass forming ability of Ni-Pd-P system, a DFT study on crystalline related clusters

In order to investigate the influence of Si in the glass forming ability of Pd-Ni-P based bulk metallic glasses, the topological and electronic structure of stoichiometry related crystals is explored using density functional theory. The results indicate that Si based clusters based on a rich Pd environment with a symmetric configuration of the transition metal are the most stable, while P prefers a Ni rich environment with an asymmetric arrangement of the transition metals. Si tends to be at the center of the clusters, while in general the P atoms present a displacement toward some of the Ni atoms. The coordination of Si in rich Ni crystals is always higher than the one observed for P atoms. Also, the inclusion of Si induces a local pressure field in a radius of 14 Å leading to a disordered displacement of P from the equilibrium positions. The favoring of different competing crystals by adding Si, as well as the local pressure effect, suggests a mechanism on how devitrification is suppressed.