Short-range Atomic Topology of Ab initio Generated Amorphous PdSi Alloys

TL;DR

This study uses ab initio molecular dynamics to analyze the atomic structure of amorphous Pd-Si alloys, revealing structural features and changes near specific compositions that may relate to magnetic properties.

Contribution

It provides detailed atomic topology of amorphous Pd-Si alloys generated by ab initio simulations, including correlation functions and structural motifs, which were previously not systematically reported.

Findings

Reproduces experimental pair correlation functions

Identifies structural changes near Pd86.66Si13.34 composition

Reports explicit amorphous topologies

Abstract

Since the pioneering efforts of Duwez and coworkers in 1965, when a solid amorphous phase of Pd-Si ($a$-PdSi) was obtained in the vicinity of the eutectic concentration, much work has been done. However, some points related to the atomic structures remain to be systematized. In this work, 8 amorphous Pd$_{100-c}$Si$_{c}$ alloys (c = 2.5, 5, 10, 13.34, 15, 17.5, 20, and 22 at %) were generated by molecular dynamics $ab$ $initio$ simulations; the short-range structure is analyzed using several correlation functions, like Pair Distribution Functions, reduced Pair Distribution Functions, Plane Angle Distribution Functions. Other related properties, like nearest-neighbors and some Frank-Kasper polyhedra are reported. The generated samples correctly reproduce the scarce experimental pair correlation functions that are reported in the literature. An unexpected outcome is the appearance of structural changes in the neighborhood of Pd$_{86.66}$Si$_{13.34}$, which may be related to the magnetic changes reported in the liquid and amorphous Pd-Si alloys previously reported. The explicit amorphous topologies are reported.