Second-Nearest-Neighbor Correlations from Connection of Atomic Packing Motifs in Metallic Glasses and Liquids.

Jun Ding,Robert O Ritchie,Evan Ma,Mark Asta

doi:10.1038/srep17429

Abstract

Using molecular dynamics simulations, we have studied the atomic correlations characterizing the second peak in the radial distribution function (RDF) of metallic glasses and liquids. The analysis was conducted from the perspective of different connection schemes of atomic packing motifs, based on the number of shared atoms between two linked coordination polyhedra. The results demonstrate that the cluster connections by face-sharing, specifically with three common atoms, are most favored when transitioning from the liquid to glassy state, and exhibit the stiffest elastic response during shear deformation. These properties of the connections and the resultant atomic correlations are generally the same for different types of packing motifs in different alloys. Splitting of the second RDF peak was observed for the inherent structure of the equilibrium liquid, originating solely from cluster connections; this trait can then be inherited in the metallic glass formed via subsequent quenching of the parent liquid through the glass transition, in the absence of any additional type of local structural order. Increasing ordering and cluster connection during cooling, however, may tune the position and intensity of the split peaks.

Highlights

Metallic glasses (MGs) were first discovered some five decades ago but are still of significant current interest because of their unique structure and properties[1,2,3,4]
At length scales longer than that typically described by this short-range order (SRO), i.e., beyond the first NNs corresponding to the first peak in the radial distribution function (RDF), characterizing the atomic structure of these materials becomes even more complex[9,10,20,21,22,23,24,25,26,27,28,29,30]
Before one can establish the nature of extended order, a useful step is to first understand the atomic correlations with atoms in the second nearest neighbor shell

Summary

Introduction

Metallic glasses (MGs) were first discovered some five decades ago but are still of significant current interest because of their unique structure and properties[1,2,3,4]. Before one can establish the nature of extended order (such as those postulated in these models, which most likely vary from one alloy system to another), a useful step is to first understand the atomic correlations with atoms in the second nearest neighbor shell These latter correlations are reflected by the second peak in the RDFs of MGs and their parent SLs. As the distances characteristic of the second peak are just beyond the short-range scale, i.e., the packing of atoms in the NN shell constituting the motif/cluster above, the second-NN correlations can be a useful starting point for the characterization of medium-range order.

Objectives

Methods

Results