Effect of the Free Volume on the Electronic Structure of Cu70Zr30 Metallic Glasses.

Simon Evertz,Jochen M Schneider

doi:10.3390/ma13214911

Abstract

While it is accepted that the plastic behavior of metallic glasses is affected by their free volume content, the effect on chemical bonding has not been investigated systematically. According to electronic structure analysis, the overall bond strength is not significantly affected by the free volume content. However, with an increasing free volume content, the average coordination number decreases. Furthermore, the volume fraction of regions containing atoms with a lower coordination number increases. As the local bonding character changes from bonding to anti-bonding with a decreasing coordination number, bonding is weakened in the volume fraction of a lower coordination number. During deformation, the number of strong, short-distance bonds decreases more for free volume-containing samples than for samples without free volume, resulting in additional bond weakening. Therefore, we show that the introduction of free volume causes the formation of volume fractions of a lower coordination number, resulting in weaker bonding, and propose that this is the electronic structure origin of the enhanced plastic behavior reported for glasses containing free volume.

Highlights

Plastic deformability is crucial for structural applications of metallic glasses [1]
The goal of this study is to understand the effect of free volume on the electronic structure and chemical bonding based on ab initio calculations by systematically increasing the free volume content of Cu70 Zr30
A systematic, ab initio calculation-based comparison pf Cu70 Zr30 metallic glasses with free volume contents varying from 0.0% to 4.6% revealed that the overall bond strength based on the integrated

Summary

Introduction

Plastic deformability is crucial for structural applications of metallic glasses [1]. Increasing the free volume content has been proposed to enhance the plastic deformation of metallic glasses and is often referred to as “structural rejuvenation” [2]. An enhanced free volume content was reported to induce work hardening and enable stable plastic deformation [3]. While the literature often focusses on free volume-induced changes in internal energy [2,7,8,9,10] and topology [3,11,12,13], the effect of free volume on the electronic structure has been overlooked far. The goal of this study is to understand the effect of free volume on the electronic structure and chemical bonding based on ab initio calculations by systematically increasing the free volume content of Cu70 Zr30

Objectives

Methods

Results

Conclusion