Can Symmetric Tilt Grain Boundaries Represent Polycrystals?

TL;DR

This paper challenges the common practice of using high-symmetry tilt grain boundaries as proxies for polycrystals, showing they fail to represent the diversity of real grain boundary environments, especially for solute segregation.

Contribution

It provides a quantitative comparison demonstrating that low-symmetry grain boundaries are necessary to accurately model polycrystalline materials.

Findings

High-symmetry boundaries do not capture the diversity of polycrystalline environments.

Using low-symmetry boundaries improves the accuracy of property predictions.

Common assumptions about boundary symmetry may lead to incorrect insights.

Abstract

Grain boundaries control a wide variety of bulk properties in polycrystalline materials, so simulation methods like density functional theory are routinely used to study their structure-property relationships. A standard practice for such simulations is to use compact, high-symmetry (coincident site lattice) boundaries as representatives of the much more complex polycrystalline grain boundaries. In this letter, we question this practice by quantitatively comparing the spectra of atomic sites and properties amongst grain boundaries. We show, using solute segregation as an example property, that highly symmetric tilt boundaries (with {\Sigma} values less than 10) will fail to capture polycrystalline grain boundary environments, and thus lead to incorrect quantitative and qualitative insights into their behavior.