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

Tin dioxide (SnO) is one of the transparent conductive oxides that has aroused the interest of researchers due to its wide range of applications. SnO 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 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, 3̅, 4/, and are dynamically unstable. As far as we know, no previous research has investigated the electronic properties of SnO polymorphs from the hybrid functional of Heyd, Scuseria, and Erhzerhof (HSE06) except 4/, 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 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 -SnO 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, rutile is a promising candidate for many applications; however, we investigated the feasibility of the remaining polymorphs for practical applications.