Hybrid density functional study of electronic and optical properties of phase change memory material: $\mathrm{Ge_{2}Sb_{2}Te_{5}}$

TL;DR

This study employs hybrid density functional (HSE06) to accurately investigate the electronic, structural, and optical properties of $ ext{Ge}_2 ext{Sb}_2 ext{Te}_5$, a key phase change memory material, aligning well with experimental data.

Contribution

It demonstrates the effectiveness of HSE06 in predicting properties of $ ext{Ge}_2 ext{Sb}_2 ext{Te}_5$ and reveals complex charge distributions beyond simple ionic models.

Findings

HSE06 provides band gap values close to experimental data.

Hybrid functional slightly overestimates the 'C' parameter.

Charge analysis shows complex charge distribution, not explained by ionic models.

Abstract

In this article, we use hybrid density functional (HSE06) to study the crystal and electronic structures and optical properties of well known phase change memory material $\mathrm{Ge_{2}Sb_{2}Te_{5}}$. We calculate the structural parameters, band gaps and dielectric functions of three stable structures of this material. We also analyze the electron charge distribution using the Bader's theory of charge analysis. We find that hybrid density functional slightly overestimate the value of 'C' parameter. However, overall, our results calculated with the use of hybrid density functional (HSE06) are very close to available experimental values than calculated with the use of PBE functional. Specifically, the electronic band gap values of this material calculated with HSE06 are in good agreement with the available experimental data in the literature. Furthermore, we perform the charge analysis and find that naive ionic model fails to explain the charge distribution between the constituent atoms, showing the complex nature of this compound.