Atomistic Green's Function Method supported by ab initio Calculations : Application to phonon transport in ZnO and ZnS

TL;DR

This paper introduces a parameter-free method combining atomistic Green's function with ab initio calculations to accurately model ballistic phonon transport in materials like ZnO and ZnS, aiding thermoelectric device design.

Contribution

The novel approach integrates ab initio force constants with AGF to compute phonon transport without empirical parameters, applied to specific materials for the first time.

Findings

Transmission functions vary with transport direction.

ZnO/ZnS interface may block phonons effectively.

Potential to enhance thermoelectric efficiency.

Abstract

We present an approach to calculate ballistic phonon transport that combines the atomistic Green's function (AGF) method with ab initio results. For the inter atomic potential we use the harmonic approach. The equilibrium positions of the atoms and the inter atomic force constants(ifcs) are calculated using the ABINIT program package, which is based on density functional theory. Therefore, the presented approach is parameter free. From the Green's function of the system we determine the density of states as well as the transmission function. The thermal conductance is obtained within the linear response regime. We apply this approach to bulk ZnO and bulk ZnS. Transmission functions for different transport direction for each material are presented. A comparison of the transmission function shows, that a ZnO/ZnS interface could be a promising phonon blocker. Adding such interfaces in ZnO or ZnS based thermoelectric devices could therefore increase the figure of merit.