Finding merit in dividing neighbors

TL;DR

This paper explores how structural distortions in rocksalt-structured IV-VI semiconductors influence their thermoelectric properties, highlighting the role of neighbor division in symmetry lowering and thermoelectric efficiency.

Contribution

It provides a detailed analysis of how neighbor division and symmetry breaking in rocksalt structures affect thermoelectric performance, offering insights into material design.

Findings

Rhombohedral and orthorhombic distortions divide neighbors, affecting symmetry.

Structural competition influences thermoelectric figure of merit.

Lower symmetry structures are linked to enhanced thermoelectric properties.

Abstract

The IV-VI binary semiconductors and and column V elements crystalize in one of the three varieties derived from the cubic rocksalt structure. The rocksalt structure can be seen as a network of interpenetrating octahedra with an atom at the center of each octahedron and its six nearest neighbors at the vertices. What drives lower symmetry is the problem of placing ten electrons along three perpendicular axes with six equivalent neighbors. Rhombohedral and orthorhombic distortions divide the six immediate neighbors in two distinct sets of first neighbors and second neighbors. This structural competition is at the origin of the the remarkable thermoelectric figure of merit in SnSe and PbTe.