Systematic Study on Electronic, Mechanical, and Thermal Transport Properties of Germanium Antimony Selenide Telluride Alloy by a First-Principles Approach

Abstract

Ge 2 Sb 2 Se 4 Te alloy has most recently exhibited its outstanding optical properties for non-volatile photonic storage applications, while its electrical and thermal transport properties were rarely reported, thus limiting its application versatility. To overcome the above issue, we performed a detailed and systematic study on the electrical, mechanical, and thermal transport properties of Ge 2 Sb 2 Se 4 Te alloy using first-principles calculations. The results show that Young's modulus and shear modulus of Ge 2 Sb 2 Se 4 Te are anisotropic, originating from its layered crystal structure. Besides, Poisson's ratio suggests that the in-plane bonding of Ge 2 Sb 2 Se 4 Te was mainly ionic-covalent bonding, while the out-ofplane bonding was of van der Waals (vdW) interaction character. The chemical bond difference between in-plane and out-of-plane directions induces strong phonon anharmonicity and phonon thermal transport anisotropy. Therefore, layered Ge 2 Sb 2 Se 4 Te exhibited low phonon group velocity and short phonon lifetime, resulting in encouragingly low lattice thermal conductivities of 4.45, 3.54, and 0.41 W/mK along the x-axis, y-axis, and z-axis at 300 K, respectively. Furthermore, the calculated electronic structure revealed the metallicity character of Ge 2 Sb 2 Se 4 Te alloy without a pronounced bandgap, which made this material applicable to thermal insulation materials rather than traditional thermoelectric materials. This work was useful to promote the application of Ge 2 Sb 2 Se 4 Te in the field of engineering thermal management and storage devices based on the optical-thermal mechanism. KEYWORDS: Ge 2 Sb 2 Se 4 Te, lattice thermal conductivity, engineering thermal management, first-principles calculations, thermoelectric, phonon