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

Ge2Sb2Se4Te alloy hasmost recentlyexhibited its outstanding optical properties for non-volatile photonicstorage applications, while its electrical and thermal transport propertieswere rarely reported, thus limiting its application versatility. Toovercome the above issue, we performed a detailed and systematic studyon the electrical, mechanical, and thermal transport properties ofGe(2)Sb(2)Se(4)Te alloy using first-principlescalculations. The results show that Young's modulus and shearmodulus of Ge2Sb2Se4Te are anisotropic,originating from its layered crystal structure. Besides, Poisson'sratio suggests that the in-plane bonding of Ge2Sb2Se4Te was mainly ionic-covalent bonding, while the out-of-planebonding was of van der Waals (vdW) interaction character. The chemicalbond difference between in-plane and out-of-plane directions inducesstrong phonon anharmonicity and phonon thermal transport anisotropy.Therefore, layered Ge2Sb2Se4Te exhibitedlow phonon group velocity and short phonon lifetime, resulting inencouragingly low lattice thermal conductivities of 4.45, 3.54, and0.41 W/mK along the x-axis, y-axis,and z-axis at 300 K, respectively. Furthermore, thecalculated electronic structure revealed the metallicity characterof Ge2Sb2Se4Te alloy without a pronouncedbandgap, which made this material applicable to thermal insulationmaterials rather than traditional thermoelectric materials. This workwas useful to promote the application of Ge2Sb2Se4Te in the field of engineering thermal management andstorage devices based on the optical-thermal mechanism.