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

Ge2Sb2Se4Te 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
Ge2Sb2Se4Te alloy using first-principles
calculations. The results show that Young’s modulus and shear
modulus of Ge2Sb2Se4Te are anisotropic,
originating from its layered crystal structure. Besides, Poisson’s
ratio suggests that the in-plane bonding of Ge2Sb2Se4Te was mainly ionic-covalent bonding, while the out-of-plane
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 Ge2Sb2Se4Te 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 Ge2Sb2Se4Te 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 Ge2Sb2Se4Te in the field of engineering thermal management and
storage devices based on the optical-thermal mechanism.