First-Principles Exploration into the Physical and Chemical Properties of Certain Newly Identified SnO 2 Polymorphs.

Tin dioxide (SnO 2 ) is one of the transparent conductive oxides that has aroused the interest of researchers due to its wide range of applications. SnO 2 exists in a variety of polymorphs with different atomic structures and Sn-O connectivity. However, there are no comprehensive studies on the physical and chemical properties of SnO 2 polymorphs. For the first time, we investigated the structural stability and ground-state properties of 20 polymorphs in the sequence of experimental structures determined by density functional theory. We used a systematic analytical method to determine the viability of polymorphs for practical applications. Among the structurally stable polymorphs, Fm 3̅ m , I 4 1 / amd , and Pnma-II are dynamically unstable. As far as we know, no previous research has investigated the electronic properties of SnO 2 polymorphs from the hybrid functional of Heyd, Scuseria, and Erhzerhof (HSE06) except P 4 2 / mnm , with calculated band gap values ranging from 2.15 to 3.35 eV. The dielectric properties of the polymorphs have been reported, suggesting that SnO 2 polymorphs are also suitable for energy storage applications. The bonding nature of the global minimum rutile structure is analyzed from charge density, charge transfer, and electron localization function. The Imma -SnO 2 polymorph is mechanically unstable, while the remaining polymorphs met all stability criteria. Further, we calculated Raman and IR spectra, elastic moduli, anisotropic factors, and the direction-dependent elastic moduli of stable polymorphs. Although there are many polymorphic forms of SnO 2 , rutile is a promising candidate for many applications; however, we investigated the feasibility of the remaining polymorphs for practical applications.