Order evolution from a high-entropy matrix: understanding and predicting paths to low temperature equilibrium

TL;DR

This paper investigates how synthesis conditions and boundary factors influence the evolution of high-entropy inorganic compounds into ordered structures, using a combination of experimental and computational methods to predict their structural pathways.

Contribution

It introduces a comprehensive framework combining microscopy, spectroscopy, DFT, and phase field modeling to understand and predict order evolution in high-entropy materials.

Findings

Identification of synthesis and boundary conditions affecting order formation.

Demonstration of nano-structure evolution in Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O.

Validation of predictive modeling for macrostate spectrum.

Abstract

Interest in high-entropy inorganic compounds originates from their ability to stabilize cations and anions in local environments that rarely occur at standard temperature and pressure. This leads to new crystalline phases in many-cation formulations with structures and properties that depart from conventional trends. The highest-entropy homogeneous and random solid-solution is a parent structure from which a continuum of lower-entropy offspring can originate by adopting chemical and/or structural order. This report demonstrates how synthesis conditions, thermal history, and elastic and chemical boundary conditions conspire to regulate this process in Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O, during which coherent CuO nano-tweeds and spinel nano-cuboids evolve. We do so by combining structured synthesis routes, atomic-resolution microscopy and spectroscopy, density functional theory, and a phase field modeling framework that accurately predicts the emergent structure and local chemistry. This establishes a framework to appreciate, understand, and predict the macrostate spectrum available to a high-entropy system that is critical to rationalize property engineering opportunities.