# Atomistic study of an ideal metal/thermoelectric contact: the full-Heusler/half-Heusler interface

## TL;DR

This study uses first-principles calculations to analyze the structural and electronic properties of full-Heusler/half-Heusler interfaces, revealing their potential as low-resistance, stable electrical contacts for thermoelectric devices.

## Contribution

It provides a theoretical investigation of the atomic-scale properties of ideal metal/thermoelectric contacts, highlighting the potential of full-Heusler/half-Heusler interfaces for improved thermoelectric performance.

## Key findings

- HfNi₂Sn/HfNiSn interface exhibits very low contact resistivity.
- The interface shows almost ohmic behavior across various temperatures and doping levels.
- Full-Heusler compounds can serve as stable, nearly ideal electrical contacts for half-Heusler thermoelectric materials.

## Abstract

Half-Heusler alloys such as the (Zr,Hf)NiSn intermetallic compounds are important thermoelectric materials for converting waste heat into electricity. Reduced electrical resistivity at the hot interface between the half-Heusler material and a metal contact is critical for device performance, however this has yet to be achieved in practice. Recent experimental work suggests that a coherent interface between half-Heusler and full-Heusler compounds can form due to diffusion of transition metal atoms into the vacant sublattice of the half-Heusler lattice. We study theoretically the structural and electronic properties of such an interface using a first-principles based approach that combines {\it ab initio} calculations with macroscopic modeling. We find that the prototypical interface HfNi$_2$Sn/HfNiSn provides very low contact resistivity and almost ohmic behavior over a wide range of temperatures and doping levels. Given the potential of these interfaces to remain stable over a wide range of temperatures, our study suggests that full-Heuslers might provide nearly ideal electrical contacts to half-Heuslers that can be harnessed for efficient thermoelectric generator devices.