# Rationalizing Patterns in the Cation Ordering, Geometric Distortion, and Electronic Properties of a Class of I–V–VI2 Chalcogenide Semiconductors

## TL;DR

This paper explores how atomic arrangements in chalcogenide semiconductors affect their electronic properties, aiming to improve solar energy materials.

## Contribution

A novel model connects atomic sequences to bonding motifs, explaining structural diversity and enabling property tuning in I–V–VI2 compounds.

## Key findings

- Structural variety in I–V–VI2 compounds arises from distinct cation ordering and geometric distortion patterns.
- Local bonding motifs (2-center 2-electron and 3-center 4-electron) influence electronic properties like band gaps.
- The model provides a framework to rationally design and tune optoelectronic properties of chalcogenide semiconductors.

## Abstract

Chalcogenide semiconductors
are of interest as light
absorbers
for solar energy conversion applications. To fully realize their potential,
it is crucial to understand how to tune the optoelectronic properties
of these compounds through changes in their composition and atomic
structure. In this paper, we use density functional theory calculations
as a guide to understanding and tuning a class of ABX2 (I–V–VI2) compounds (A = Li, Na, K, Rb; B = As, Sb, Bi; X = S, Se).
While these compounds can all be viewed as superstructures of NaCl,
they have remarkable variety in their patterns of cation ordering
and geometric distortion. By exploring a novel model that connects
the sequences of atoms along B–X bond axes to local bonding
motifs (2-center 2-electron and 3-center 4-electron), we rationalize
the structural variety in this class of compounds and suggest how
it can be leveraged to tune their properties such as band gap.