Design Rules and Discovery of Face-Sharing Hexagonal Perovskites

TL;DR

This paper develops quantitative design principles for stabilizing face-sharing hexagonal perovskites, enabling targeted discovery of new materials with potential for novel ferroic properties, especially among sulfides due to their covalency and flexibility.

Contribution

It introduces a phase-space mapping approach using an electronegativity-corrected tolerance factor to predict stable face-sharing hexagonal perovskites, expanding the design framework for these underexplored materials.

Findings

Identified thresholds separating hexagonal and cubic phases based on structural parameters.

Sulfides exhibit greater compositional flexibility due to increased covalency.

Predicted new thermodynamically stable face-sharing perovskite compounds.

Abstract

Hexagonal perovskites with face-sharing octahedral connectivity are an underexplored class of materials. We propose quantitative design principles for stabilizing face-sharing ABX3 hexagonal perovskites based on a comparative analysis of oxides and sulfides. By mapping structural preferences across a phase-space defined by an electronegativity-corrected tolerance factor and the Shannon radius of the A-site cations, we identify distinct thresholds that separate hexagonal phases from competing cubic polymorphs having corner-sharing octahedral connectivity. Our analysis reveals that sulfides differ significantly from oxides due to the increased covalency of the transition metal-sulfur bonds, which enables broader compositional flexibility. Applying these principles, we predict a set of thermodynamically formable ABO3 and ABS3 compounds that are likely to adopt face-sharing octahedral connectivity. These findings establish a predictive framework for designing hexagonal perovskites, highlighting sulfides as promising candidates for obtaining quasi-one-dimensional materials having transition-metal cations for novel ferroic phenomena.