Electronic, optical and thermal properties of the hexagonal and fcc Ge2Sb2Te5 chalcogenide from first-principle calculations

TL;DR

This study uses first-principles calculations to analyze the electronic, optical, and thermal properties of hexagonal and fcc Ge2Sb2Te5 chalcogenide, aligning well with experimental data and providing insights into its transport and thermal behavior.

Contribution

It offers a comprehensive computational analysis of Ge2Sb2Te5's properties, including electronic structure, optical constants, and phonon-related thermal characteristics, filling gaps in experimental data.

Findings

Density of states matches experimental results

Optical properties capture key experimental features

Thermal conductivity and heat capacity agree with measurements

Abstract

We present a comprehensive computational study on the properties of face-centered cubic and hexagonal chalcogenide Ge2Sb2Te5. We calculate the electronic structure using density functional theory (DFT); the obtained density of states (DOS) compares favorably with experiments, also looking suitable for transport analysis. Optical constants including refraction index and absorption coefficient capture major experimental features, aside from an energy shift owed to an underestimate of the band gap that is typical of DFT calculations. We also compute the phonon DOS for the hexagonal phase, obtaining a speed of sound and thermal conductivity in good agreement with the experimental lattice contribution. The calculated heat capacity reaches ~ 1.4 x 106 J/(m3 K) at high temperature, in agreement with experimental data, and provides insight into the low-temperature range (< 150 K), where data are unavailable.