Citation: Behera, D.; Manzoor, M.; Sharma, R.; Salah, M.M.; Stich, I.; Mukherjee, S.K. A Comprehensive First-Principles Investigation of SnTiO 3 Perovskite for Optoelectronic and Thermoelectric Applications. Crystals 2023, 13, 408. https:// doi.org/10.3390/cryst13030408 Academic Editors: Zhifang Shi and Guang Yang Received: 28 January 2023 Revised: 14 February 2023 Accepted: 16 February 2023 Published: 27 February 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). crystals Article A Comprehensive First-Principles Investigation of SnTiO 3 Perovskite for Optoelectronic and Thermoelectric Applications Debidatta Behera 1 , Mumtaz Manzoor 2 , Ramesh Sharma 3, * , Mostafa M. Salah 4, * , Ivan Stich 2 and Sanat Kumar Mukherjee 1 1 Department of Physics, Birla Institute of Technology, Mesra, Ranchi 835215, India 2 Institute of Informatics, Slovak Academy of Sciences, Dubravska cesta 9, 845 07 Bratislava, Slovakia 3 Department of Applied Science, Feroze Gandhi Institute of Engineering and Technology, Raebareli 835215, India 4 Electrical Engineering Department, Future University in Egypt, Cairo 11835, Egypt * Correspondence: sharmadft@gmail.com (R.S.); mostafa.abdulkhalek@fue.edu.eg (M.M.S.) Abstract: In this work, the structural, elastic, electronic, thermodynamic, optical, and thermoelectric properties of cubic phase SnTiO 3 employing first-principles calculation are examined. The calculations of all parameters via various potentials such as LDA, PBE-GGA, WC-GGA, PBEsol-GGA, mBJ-GGA, nmBJ-GGA, and HSE are performed. The computed band structure yields an indirect bandgap of 1.88 eV with the HSE approach. The optical parameters have been evaluated through absorption, dispersion, and loss function. For cubic phase SnTiO 3 , the maximum absorption coefficient α(ω) is 173 × 10 4 (cm) −1 at high energy region 9 eV. The thermoelectric properties of the SnTiO 3 have been explored by the Seebeck coefficient, thermal conductivity, and power factor employing the BoltzTrap code with temperature and chemical potential. Furthermore, the thermodynamic quantities under high pressure (0–120 GPa) and temperature (0–1200 K) are also calculated. Keywords: DFT; FP-LAPW; electronic properties; elastic properties; optical properties; thermoelectric properties; thermodynamic properties 1. Introduction Over the last few decades, because of the rising need for energy around the world, the scientific community has become more interested in discovering new renewable energy sources. Owing to their excellent thermal efficiency, perovskite oxide compounds are useful in optoelectronic and thermoelectric usages such as thermoelectric coolers, thermo- couples, etc. In the present scenario, perovskite ferroelectric materials are widely used in applications of electronics, IR sensors, non-volatile memories, dielectric properties, optical waveguides, and substrates for high-T C superconductor growth [1,2]. Further- more, perovskite compounds exhibit distinct properties such as low optical loss factor, high absorption in the invisible region, direct bandgap, etc. [1,3,4]. Due to these unique characteristics, semiconducting perovskites are promising candidates for usage in elec- tronic devices that include solar cells, photodetectors, etc. [5–7]. To address the primary drawbacks of Pb-based perovskites, namely their toxicity and lack of chemical stability, numerous alternative perovskite compounds have recently been identified and synthesized. Gonjal et al. investigated Nb doped SrTiO 3 and reported its thermoelectric properties [8]. According to these findings, lead-based perovskites can be effectively replaced with Sn- based perovskites. SnTiO 3 is a potential Pb-free ferroelectric material with a high dielectric constant and ferroelectric polarization in theory. Nevertheless, most theoretical studies on SnTiO 3 materials focus only on their physical characteristics and strong polarization effects in the ferroelectric phase. The electrical and optical characteristics of the cubic structure of SnTiO 3 have undergone extensive theoretical and experimental studies [9–18]. The ferroelectric properties of the SnTiO 3 were reported by Parker et al. and others [19–21]. Crystals 2023, 13, 408. https://doi.org/10.3390/cryst13030408 https://www.mdpi.com/journal/crystals