Chemical Perspectives of Heteroanionic Compounds and a Potential Playground for Multiferroics

Abstract

Heteroanionic compounds, which host two or more different anions, have appeared as a huge family of functional materials. Different from polyanionic compounds, there is no direct connection between anions within heteroanionic compounds. The connectivity between anions and central atoms constitutes various distorted basic building units (BBU). The linkage between BBUs further promotes the structural flexibility of heteroanionic compounds. Considering the diverse bonding nature of anion-metal interactions, which originate from the various physical and chemical properties of anions, explains the existence of many important applications of heteroanionic compounds. In this short review, we summarize the synthesis, structure examples, and physical applications of selected heteroanionic compounds. From a synthesis perspective, a deep understanding of crystal growth mechanisms and a better-controlled growth process should be emphasized in future research. The interactions between distinct anions and other featured elements such as elements with lone electron pairs, d0 and d10 transition metals, etc., or other systems such as high entropy systems would further promote more interesting applications. Heteroanionic compounds, which exhibit comparable structure features with known multiferroics, might be a new paradise for discovering multiferroics. Machine learning and quickly developed calculation capabilities can also aid the study of heteroanionic compounds by understanding growth mechanisms, searching for new compounds, and targeting specific properties.