Electronic, mechanical, and optical properties of Ruddlesden-Popper perovskite sulfides: First principle calculation

Abstract

In the present paper we have investigated the electronic structure of some orthorhombic A₃X₂S₇ (X = Ti, Zr, and Hf) compounds based on the density functional theory. Then we extend the Ruddlesden–Popper (RP) A₃X₂S₇ sulfides and examine how ferroelectricity is induced by coupled octahedral rotation modes. The mechanical and optical properties have also been computed. The second-order elastic constants have been calculated, and the other related quantities have also been estimated in the present work. The band gap trend in A₃X₂S₇ can be understood from the nature of their electronic structures. The obtained electronic band structure for Ba₃Zr₂S₇ and Ba₃Hf₂S₇ compounds are semiconductor in nature, and the Ba₃Ti₂S₇ compound is also semi-metal. Similar to ferroelectric oxides, there is a pronounced hybridization of electronic states between X-site cations and anions in A₃X₂S₇. Based on the obtained electronic structures, we further calculate the frequency-dependent dielectric function and other optical functions in different phases.

KEYWORDS:

• Ab initio calculation
• electronic structure
• mechanical properties
• optical properties

Funding

This work is supported by the projects DPT-HAMIT and NATO-SET-193, and one of the authors (Ekmel Ozbay) also acknowledges partial support from the Turkish Academy of Sciences.